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A. AGASSIZ.

HARVARD UNIVERSITY.

LIBRARY

OF THE

MUSEUM

OF GOMPAEATIVE

GIFT OF

ALEX. AGASSIZ.

ZOOLOGY

Mac

7 /S77

_-JL.'

THE

KAY S C I E T Y.

INSTITUTED MDCCCXLIV.

3^

LONDON

MDCCCLXII.

^^l

-?

INTRODUCTION

TO THE STUDY OF THE

F R A M I N I F E R A

BY

WILLIAM ]]. CARPENTER, M.D., F.R.S., F.L.S.. F.CI.S.,

KEGISTRJE OF THE UNITEKSITY OF LONDON,
ETC.! ETC.

ASSISTED BY

WII.LIAM K. PARKEE, ESQ.,

AND

T. RUPEET JONES, ESQ., E.G.S.

LONDON:

PUBLISHED FOR THE RAY SOCIETY BY
ROBERT HARDWICKE, 193, PICCADILLY.

MDCCCLXII.

MCZ LIBRARY
HARVARD UNIVERSITY
CAMBRIDGE. MA USA

PKINTED BT J. E. ADLARD,
BABTHOLOWEW CLOSE.

P R E E A C E.

When, some years since, I undertook to prepare for the Ray Society an outline view of
the structure, physiology, and systematic arrangement of the Foraminifera generally, I had no
idea of contributing anything else than an introduction to my friend Prof. W. C. Williamson's
' Recent Foraminifera of Great Britain.' With the progress of my own researches, however,
I came more and more strongly to feel how unsatisfactory are the results of the method
pursued by M. D'Orbigny and by those who have followed his lead, both as regards the
multiplication of species, the distinction of genera, and the grouping of these genera into
families and orders. I found, moreover, that notwithstanding the dissimilarity between the
lines of inquiry pursued by myself on the one hand and by my friends Messrs. Parker and
Rupert Jones on the other, they led to conclusions most singularly accordant. My own studies
had been restricted to a hmited range of types (for the most part collected by Mr. Jukes on
the Australian coast and by Mr. Cuming in the Philippine Seas), which included, however, all
the most complex and highly developed forms of recent Foraminifera ; and I had specially de-
voted myself to the elucidation of their structure and physiology, and to the careful comparison
of their numerous varietal forms. Theirs, on the other hand, had involved the comparison of
the zoological characters of vast numbers of representatives of nearly all the generic types
of the group, fossil as well as recent, brought together from various parts of the
world, from various depths in the ocean, and from various geological formations ; but had
not been prosecuted with the same minuteness in regard to the details of internal struc-
ture or to physiological -relations. Yet we had all been alike brought to recognise—

VI PREFACE.

(1) the extreme latitude of the rm>ge of variation in this group, which breaks down in ahnost
every instance the boundaries wliieh it has Ijcen attempted to erect between species ; (2) the
necessity of a hke abolition of the divisions between many reputed genera which have been
erected on an equally insecure basis ; (3) the completely unnatural character of any system
which makes a fundamental division between the INIonothalamous and the Polythalamous
types, and which adopts Plan of Growth (that is, the geometrical arrangement of aggrega-
tions of successive segments) as the basis of the subdivision of the PoJgthalamia into orders; and
(4) the fundamental importance, in the determination of the true affinities of the several
generic types, of all that relates to the physiological condition of the animal, especially the
texture of the shell, and the peculiarities of conformation which characterise its individual
segments.

Not only, moreover, did there prove to be this complete harmony in our general results,
but there was also a singular unity in the aggregate of the work we had respectively accom-
plished, each portion being, so to speak, the complement of the other ; so that, on comparing
notes, we found that we had between us pretty thoroughly investigated the entire group.
Hence I was led to propose to the Council of the Ray Society an enlargement of my original
plan, so as to include the results of my friends' labours, and to render the whole an expression
of our joint views. This I did in the expectation that wo might associate ourselves together
in such a manner that whilst the general plan and a part of the details of its working out
would rest with me, a large share in the execution would be taken by my coadjutors. We
soon found, however, that it would be more conducive both to unity of design and to com-
pleteness of effect for the whole to be wrought out by myself; and it has been by the
necessity which thence arose for my personal study of many types with which I was previously
but little or not at all acquainted, that the delay in the production of the work has for the
most part been occasioned. The materials for this study have been most liberally supplied to
me by Messrs. Parker and Rupert Jones ; and as to many types which they had previously
made the object of special researches (such as the Milioline, Nodosarine, Texfidarine, and
Botali/ie grou\)s'), I have found that I had nothing to do but to accept their well-considered and
satisfactory conclusions. In certain other cases, especially in regard to the genus Bacii/hpora
and to that collection of forms which they had described under the generic designation
Orhitolina (here referred to the genera Tinoporus and Pafellina), my own investigation of the
materials which they have placed in my hands has led me to results in some respects different
from those which they had published ; but as they have seen reason to accept my modifica-
tions, the account of those types here given may be regarded as not less theirs than mine. In
regard to the genus Nummidina, the most important cf all Poraminifera in a geological point of
view, we have found ourselves in complete accordance as to the impossibility of drawing definite
lines of demarcation between its reputed species; my researches on the varietal forms of the
closely related genus Ojjercidina having led me to conclusions as to the variability of all the
differential characters on which reliance had been placed, precisely Qorresponding wdth those at

PREFACE. vii

which Messrs. Parker and Rupert Jones had arrived from a careful comparative study of the
various forms of Numntulina iiroper. I liave endeavoured, as each genus came successively
under review, to specify what share in the special investigation of its characters is due to
my coadjutors, and what has been more particularly my own ; where no such intimation is
given, we may be regarded as jointly responsible.

That our work will prove altogether satisfactory, either to the scientific or to the general
reader, is more than we can venture to anticipate. Those who look for precise definitions
will not find them here, for the simple reason that the conclusion has been forced upon us
\\\?i\,sliarply defined divisions — whether between species, genera, families, or orders — do not e.visf
amonr/ Foraminifera. And we are satisfied that any one whose study of tlie group shall have
been coextensive with our own must be ready to this extent to endorse our results. It has
been our aim, therefore, to set forth (so to speak) the fundamental " idea " of eacli of the
generic types we have adopted, rather than to attempt a precise limitation of its boundaries.
That some of our generic distinctions may be invahdated by more extended research, is just
as likely as that new generic types may present themselves among the collections from ocean
beds yet unexplored, or from geological formations as yet unscrutinised. The whole study
of this group must still be regarded as in its infancy ; and the utmost that we can hope for
this Introduction is, that it may help to give a riijht direction to that 'study. We have the
fullest confidence in the correctness of our general principles ; and shall not shrink from the
consequences of their application to our own work, however large a part of it may thereby be
superseded by something better. I have endeavoured throughout my own scientific career to
keep in view the noble character given by Schiller of the true pliilosopher, as distinguished
from the trader in science, that " he has always loved truth better than his system ; and will
gladly exchange her old and defective form for a new and fairer one." And the readiness
with which my coadjutors have accepted my amendments in the instances already alluded to,
affords the fullest assurance of their thorough participation with me in the desire, not only
that whatever is defective in our joint work may lie supplied, but that what is unsound may
be demolished, since what shall remain really good and true will then afford a firmer basis
for the future labours of otiiers.

The study of the Rhizopod type in general, and of the Foraminifera in particular, has
peculiar features of interest to the Physiologist, the Zoologist, and the Geologist.

If the views which I have expressed as to the nature and relations of their living sub-
stance be correct, that substance does not present any such differentiation as is necessary to
constitute what is commonly understood as " organization," even of the lowest degree and
simplest kind ; so that the Piiysiologist has here a case in which those vital operations which
he is accustomed to see carried on by an elaborate apparatus, are performed without any
special instruments whatever, — a little particle of apparently homogeneous jelly changing itself

viii PREFACE.

into a greater variety of forms than the fabled Proteus, laying hold of its food without
members, swallowing it without a mouth, digesting it without a stomach, appropriating its
nutritious material without absorbent vessels or a circulating system, moving from place to
place without muscles, feeling (if it has any power to do so) without nerves, propagating
itself without genital apparatus, and not only this, but in many instances forming shelly
coverings of a symmetry and complexity not surpassed by those of any testaceous animals.

Again, there are certain peculiarities about the Foramini/era which makes this group
singularly adapted for that kind of comparison, at once minute and comprehensive, amongst
large numbers of individual forms, which should be the basis of all Zoological systematization.
The size of the greater part of these organisms is so small, that many hundreds, thousands, or
even tens of thousands of them, may be contained in a pill-box ; and yet it is usually not too
minute to prevent the practised observer from distinguishing the most important peculiarities
of each individual by a hand-magnifier alone, or from dealing with it separately by a very
simple kind of manipulation. Hence the Systematist can easily select and arrange in series such
of his specimens as display sufficient mutual conformity, whilst he sets apart such as are tran-
sitional or osculant ; and an extensive range of varieties may thus be displayed within so small
a compass, that the most divergent and the connecting forms are all recognisable nearly in
the same glance. I am not acquainted with any other group of natural objects, in which such
ready comparison of great numbers of individuals can be made ; and I am much mistaken
if there be a single specimen of plant or animal, of which the range of variation has been
studied by the collocation and comparison under one survey of so large a number of specimens
as have passed under the review of Prof. Williamson, Messrs. Parker and Rupert Jones, and
myself, in our studies of the types to whicli we have respectively given our principal atten-
tion. The extraordinary diversity thus found to exist among organisms which, from the
intimacy of the relationship evinced in the gradational character of those differences as well
as in the variations observable between the several parts of one and the same organism, must
in all probability have had a common origin, seems to me unmistakeably to indicate that the
wide range of forms which this group contains is more likely to have come into existence as a
result of modifications successively occurring in the course of descent from a small number of
original types, than to have originated in the vast number of distinct creations which on the
ordinary hypothesis would be required to account for it. Hence I cannot but believe that any
systematic arrangement of Foraminifera will be of real value only in so far as its basis is laid
in a thorough knowledge of the nature and extent of those variations which every chief modifi-
cation of this type shows itself so peculiarly disposed to exhibit, and as, in building it up, the
idea of natural affinity is accepted as expressing not only degree of mutual conformity, but
actual relationship arising from community of descent more or less remote. For the occurrence
of endless gradational departures from any types which we may assume as fixed, and of links
of connection between such as present the best-marked differentiations, seems to me to point
unmistakeably to this as the only means of escape from that difficulty of indefinite multiplica-

PREFACE. ix

tion which attends the doctrine of distinct specific creations when applied to a group in which
scarcely any two individuals are alike. The case, in fact, is very analogous to that of the
relationship between the various members of the family of Mankind ; for whilst the historical
evidence of actual change in them is so incomplete, as well as so limited in its range, as to be
quite inadequate of itself to establish their community of descent, yet when that evidence is
considered in its relations to analogous facts drawn from the far greater variations of domesti-
cated animals, and to the manifold gradations by which the extreme types are connected,
physiologists of the highest eminence have felt themselves justified in accepting that commu-
nity as probable. Now the modifications which any single type of Foraminifera must have
undergone, to give origin to the whole series of diversified forms presented by that group, are
not greater in comparison with those of which we have direct evidence, than arc those which
the advocate for the specific unity of the Human Races has no hesitation in assuming as
the probable account of their present divergence.

This view of the case derives great force from the fact, which constitutes the special
feature of interest which this group has for the Geologist, that there is strong reason to
regard a large proportion of the existing Foraminifera as the Jirecf lineal descendants of those
of very ancient geological periods. This doctrine was first advanced by Prof. Ehrenberg
in regard to a considerable number of Cretaceous forms ; and has since been fully confirmed
and extended as regards the Tertiary fauna by the admirable researches of Messrs. Rupert
Jones and Parker on the Rhizopodal Fauna of the Mediterranean, as well as by my own com-
parison of the recent and fossil types of Orbitolites, OrbicuUiia, Alveolina, Ojierculbia, and
Calcarina ; and it has been shown to be applicable also to the Secondary fauna, as far back
as the upper part of the Triassic system, by the remarkable results of the investigations of
ni)'' coadjutors in regard to a well-preserved sample of it.

It can scarcely be questioned that such a continuity of the leading types of Foraminifera,
maintained through so long a series of geological periods, and the recurrence of similar
varietal departures from those types, are results of the facility with which creatures of such
low and indefinite organization adapt themselves to a great diversity of external conditions ;
so that, on the one hand, they pass unharmed through changes in those conditions which are
fatal to beings of higlier structure and more specialized constitution ; wliilst, on the other,
they undergo such modifications under the influence of those changes, as may produce a very
wide departure from the original type. Thus we have found strong reason for regarding
Temperature as exerting a most important influence in favouring not merel}^ increase of size
but specialization of development : all the most complicated and specialized forms at present
known being denizens either of tropical or of sub-tropical seas ; and many of these being-
represented in the seas of colder regions by comparatively insignificant examples, wliicli
there seems adequate reason for regarding as of the same specific types with the tropical
forms, even though deficient in some of their apparently most important features. The depth

b

X PREFACE.

of the sea-bottom seems also to affect the prevalence of particular types, and to modify the
forms under which these present themselves ; so that Messrs. Parker and Rupert Jones feel
themselves able to pronounce approximately as to the depth of water at which a deposit of
fossil Foraminifera may have been formed, by a comparison of its specific and varietal types
with those characterising various depths at the present time. And it is specially worthy of
note, that in the greatest depths of the ocean from which Foraminifera have been brought by
deep-sea soundings, these belong almost exclusively to one type, Glohigerina, one of the most
simple of the Polythalamia.

In applying the results of the foregoing inquiry to the Animal Kingdom generally, it
may be at once conceded that no other group affords anything like the same evidence, on the
one hand of the derivation of a multitude of distinguishable forms from a few primitive
types, and on the other of the continuity of those types through a vast succession of
geological epochs. But a nearly parallel case, as regards the first of these points, is pre-
sented by certain of the humbler groups of the Vegetable Kingdom ; in which it is becoming
more and more apparent, from the careful study of their life-history, not only that their range
of variation is extremely wide, but that a large number of reputed genera and species have
been erected on no better foundation than that afforded by the transitory phases of types
hitherto known only in their states of more advanced development. It would be very un-
reasonable to put aside these cases as so far exceptional, that no inferences founded upon
them can have any application to the higher forms of Animal and Vegetable life. For it is
only in the extent of their range of variation, that Foraminifera and Protojihyta differ from
Vertehrata and PUanerogamia ; and the main principle which must be taken as the basis of
the systematic arrangement of the former groups — that of ascertaining the range of variation
by an extensive comparison of indi\adual forms — is one which finds its application in every
department of Natural History, and is now recognised and acted on by all the most eminent
Botanists, Zoologists, and Palaeontologists.

The following are the general propositions which it appears to me justifiable to base on
the researches of which I have now given a resume :

a'

I. The range of variation is so great among Foraminifera, as to include not merely the
differential characters which systematists proceeding upon the ordinary methods have
accounted specific, but also those upon which the greater part of the genera of this group have
been founded, and even in some instances those of its orders.

II. The ordinary notion of species, as assemblages of individuals marked out from each
other by definite characters that have been genetically transmitted from original proto-
types similarly distinguished, is quite inapplicable to this group ; since even if the limits of
such assemblages were extended so as to include what would elsewhere be accounted genera,

PREFACE. xi

they would still be found so intimately connected by gradational links, that definite lines of
demarcation could not be drawn between them.

III. The only natural classification of the vast aggregate of diversified forms which this
group contains, will be one which ranges them according to their direction and degree of
divergence from a small number of principal family-types ; and any subordinate groupings of
genera and species which may be adopted for the convenience of description and nomencla-
ture, must be regarded merely as assemblages of forms characterised by the nature and
degree of the modifications of the original type, which they may have respectively acquired
in the course of genetic descent from a common ancestry.

IV. Even in regard to these family-types, it may fairly be questioned whether analogical
evidence does not rather favour the idea of their derivation from a common original, than
that of their primitive distinctness.

V. The evidence in regard to the genetic continuity between the Foraminifera of succes-
sive geological periods, and between those of the later of these periods and the existing in-
habitants of our seas, is as complete as the nature of the case admits.

VI. There is no evidence of any fundamental modification or advance in the Forami-
niferous type from the Palaeozoic period to the present time. The most marked transition
appears to have taken place between the Cretaceous period, whose Foraminiferous fauna
seems to have been chiefly composed of the smaller and simpler types, and the commence-
ment of the Tertiary series, of which one of the earliest members was the Nummulitic Lime-
stone, which forms a stratum of enormous thickness that ranges over wide areas in Europe,
Asia, and America, and is chiefly composed of the largest and most specialized forms of the
entire group. But these were not unrepresented in previous epociis ; and their extraordinary
development may have been simply due to the prevalence of conditions that specially favoured
it. The Foraminiferous fauna of our own seas probably presents a greater range of variety
than existed at any preceding period ; but there is no indication of any tendency to eleva-
tion towards a higher type.

VII. The general principles thus educed from the study of the Foraminifera should be
followed in the investigation of the systematic affinities of each of those great types of Animal
and Vegetable form, which is marked out by its physiological distinctness from tlie rest.
In every one of these there is ample evidence of variability ; and the limits of that varia-
bility have to be determined by a far more extended comparison than has been usually
thought necessary, before the real relations of their diS"erent forms can be even approximately
determined.

xu

PREFACE.

VIII. As it is the aim of the Physical Philosopher to determine " what are the fewest
and simplest assumptions, which being granted, the whole existing order of nature would
result,"* so the aim of the Philosophic Naturalist should be to determine how small a
number of primitive types may be reasonably supposed to have given origin by the ordinary
course of "descent with modification " to the vast multitude of diversified forms that have
peopled the globe during the long succession of geological ages, and constitute its present
Fauna and Flora.

* Mill's ' Logic/ 3rd edition, vol. i, p. 327.

TABLE OF CONTE?s'TS.

CHAPTER I.

Historical Summary.

PAGE

First Period .
Second Period

Third Period
Fourth Period

PAGE
I

7
9

CHAPTER II.
Op the Rhizopoda generally; their Organization and Physiological History:

THEIR distribution INTO SUBORDINATE GrOUPS

Order RADIOLARIA
Actinophryna
acanthometrina
polycystina
Thalassicollina

Reproduction of Rhizopoda

. 18

Order LOBOSA

18

Amosbina

. 21

Order RETICULARIA

. 21

Lieberkuhnia .

. 22

Gromia

Foraminifera

12
23

23
28
28
22
30
32

CHAPTER III.
Of THE Foraminifera generally ; their Chief Types of Structure and Modes of Growth,

AND THE PRINCIP:

Texture of the shell
Mode of increase
Intermediate skeleton
Canal-system
Separation of segments

LES TO BE FOLLOWED IN THEIR CLASSIFICATION

. 40

. 44

Plan of growth

. 53

. 48

Septal aperture

. 55

. 50

Form of septal plane .

57

. 50

Surface-marking

. 59

s . .51

General summary

. 61

Of the Sub-Ordf

R Imferforata

. 62

Genus I. Lieberkuhnia

CHAPTER IV.

Of the Family Gromida .

C3 Genus II. Gromia

Genus III. Lar/ynis

65

63
64

CHAPTER V.

Of the Family Miholida .

63

Genus I. Sqamulina

67

Geuus VII. Peneroplis

84

II. Cornuspira

68

VIII. Orhiculina

93

III. Nubemlaria

69

IX. AlveoUna

99

IV. Vertebralina

72

X. Orbitolites

105

V. Miliola .

74

XI. Dacttjlopora

127

Hauerina

81

XII. Acicularia

137

VI. Fabularia.

82

XIV

TABLE OF CONTENTS.

CHAPTER VI.
Of the Family Lituolida.

PAGE

Genus I. Trochammina . . 141 Genus II. Lititola

Genus III. ValvuUna . . . 146

PAGE

143

CHAPTER YH.
Of the Sub-Order Perforata

149

CHAPTER VIII.

Of the Family Lagexida

Genus I. Lagena

. 156

Genus III. Orthoccrina

Entosolenia

. 157

IV. Pohjmorphina

II. Nodosarina

. 159

V. Uvigerina .

Nodosaria

. 161

Cristellaria

. 162

Intermediate forms .

. 163

154

166
166
169

CHAPTER IX.

Genus I. OrbuUna.
II. Ovulites .
III. Sptrillina
Sub-Family GlobigerinjE
Genus IV. Globigerina
\. PuUenia .
VI. Spharoidina
VII. Carpenteria
Sub-Family Textularin^
Genus VIII. Textularia

IX. Chrysadilina
X. Cuneolina

Of the

Fa.mily

Globigerinida

. 171

176

Genus XI. Btdimina

. 194

179

XII. Cassidulina

. 197

180

Sub-Family Rotalin^ .

. 198

181

Genus XIII. Discorbina

. 203

181

XIV. Planorhdinu

. 206

184

XV. PulvinuUna

. 210

185

XVI. Rotalia

. 212

186

XVII. Cynibahpora

. 215

189

XVIII. Calcarina

. 216

189

XIX. Tinoporus

. 223

193

XX. PatcUina

229

193

XXI. Polytrcma

. 235

UF

Genus I. Amphistegina

the tam
. 241

II. Operculina.

. 24.7

III. Nummtdina

. 262

IV. Pohjstomella

. 276

Nonionina

. 286

CHAPTER X.
Of the Family Nummulinida.

Genus V. Heterostegina

VI. Cycloclypeus

"Vll. Orbitoides

IX. Fusulina .

238
288
292
298
304

LIST OF WOOD ENGRAVINGS.

Fig. tage

I. Coccospheres and Coccolitlis . . . . . .47

II. Composite coccospheres with attached coccoliths .... 18

ID. Diagram of Artieidinc Vertebralina . . . . . -1-9

IV. Diagram of a Frondicularian Nodosaria . . . . .49

V. Diagram of the chambered structure of Orb'itolina . . . .50

VI. Diagram of the chambered structivre of Orbitoides . . . .50

VII. Diagrammatic section of simple NautUoid shell . . . .50

VIII. Diagrammatic section of Operculina . . . . .50

IX. Vertical sections of six specimens of Operculina . . . .57

X. Vertical sections of three outer convolutions of Operculina . . .58

XI. Lateral view of Nautiloid shell, with investing convolutions . . .58

XII. Front view of Nautiloid shell, with non-investing convolutions . . .59

XIII. Front view of Nautiloid shell, with investing convolutions . . .59

XrV. Diagram of Animal of Miliola . . . . ■ .77

XV. Ideal transverse sections of Spiroloculina . . . . .77

XVI. Ideal transverse sections of Biloculina . . . . .78

XVII. Ideal transverse sections of Qiiincjueloculina . . . . .78

XVIII. Ideal transverse sections of TrilocuUna . . . . . 7fj

XIX. Section of Peneroplis through the median plane . . . .80

XX. Front views of four- specimens of Peneroplis . . . . .89

XXI. Septal planes and apertures from difterent parts oi' the same specimen oi Dendritina . 90
XXII. Simple type of Alveolina, laid open ..... 100

XXIII. Portion of internal cast of complex type of Alveolina . . . .102

XXIV. Interior of simple type of Orbitolites . . ■ ■ .108
XXV. Diagram of Dactylopora eruca ...... 128

XXVI. Diagram of Dactylopora annulus . . . . ... 129

XXVII. Diagram of Dactylopora digitata . . . . ... 1 '■")

XVI

LIST OF WOOD ENGRAVINGS.

Fig.
XXVIII. Diagram of Dactylopora chjpeina

XXIX. Diagram of Dactylopora reticulata

XXX. Diagram of Dentaline Nodosaria

XXXI. Diagram of Frondicidaria

XXXII. Various forms of RotaUna

XXXIII. Abnormal forms of CaJcarina

XXXIV. Specimens of Philippine variety of Cakarina
XXXV. Specimens of ^Mediterranean variety of Calcarina

XXXVI. Abnormal forms of Calcarina
XXXVII. Stracturc of Patellina lenticularis .
XXXVIII. Structure of Patellina Cooki

XXXIX. Irregular disposition of septa in OpercuUna .

XL. Vertical section of three outer convolutions of OpercuUna
XLI. Section of septa of OpercuUna, showing secondary pores
XLII. Vertical sections of six specimens of OpercuUna
XLIII. Septal planes of four specimens of OpercuUna
XLIV. Front view of septal plane closing-in last chamber of OpercuUna

XLV. Section of Heterosteyina through median plane
XL VI. More enlarged portion of similar section
XL VII. Vertical section of young Heterostegina

PAGE

131
132
162
164
201
217
217
217
222
232
233
253
254
254
255
258
260
289
290
291

BIBLIOGRAPHICAL REFERENCES.

Akcuiac, Vicomte d', et Haime : —

I. Description ties Animaux Fossiles du gioupe NummulUique de I'Inde. Paris, 1853.

AuEiiBACn, Dr. Leopold: —

II. Ueber die Einzelligkeit der Amo^/jeu ; in ' Siebold und Kolliker's Zeitschrift,' Band vii (185(3), p. 3ti5.

Bailey, Prof. J. W. :—
iir. On the Origin of Greensand, and its Formatioa in the Oceans of the Present Epoch ; in ' Quarterly Journal
of Microscopical Science,' vol. v (1857), p. 83.
IV. Observations on a newly discovered Animalcule {Pamphar/us) ; in ' Sdliman's Journal,' 2d series, voK xv
(1853), pp. 341— 347, and 'Quarterly Journal of Microscopical Science,' vol. i (1853), pp. 29;i— 299.

Bakker-Webb, p., and Bertiielot, J. :—
V. Histoirc Naturelle des lies Canaries. Paris, 1835-50, torn, ii, p. 123; Foraminifires par M. D'Orbiguy.

Blainville, H. D. dc : —
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xviii BIBLIOGRAPHICAL REFERENCES.

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XIX

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KoLLiKEK, Prof. Alb. : —
LVi. Das Sonnenthierchcn, Acfinophrt/s sol, bescbrieben ; in Sicbold nnd Kiilliker's ' Zeitschrift,' Band i
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Lego, M. S.:—
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LiNN.EUS, C.iK.: —

LXiii. Systema Naturse, per Regna Tria Naturae secundum Classes, Ordiues, Genera, et Species ; cum
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Macdonald, J. D. : —
LXiv. Observations on the ^licroscopic Examination of Foraminifera obtained in Deep-sea Bottoms at the
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Montagu, George : —
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MoNTFOiiT, Denys de : —
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1802-5.
Lxvii. Conchyliologie Systematique, et Classification Mcthodique des Coquilles. Paris, 1808-10.

MiiLiER, Prof. Johannes : —
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tom. iv (1839), p. 1.
LXXii. Dictiounaire Universelle d'Histoirc Naturelle, tom. v, p. 602, Art. Foramini/ires. Paris, 1844.
LXXIII. Foi-amini/cres Fossiles du Bassin Tertiaire de Vieune. Paris, 1846.

Lxxiv. Cours Elementaire de Paleontologie et de Geologic; Foramini/ires in tom. ii, fascic. i. Paris, 1852.
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new series, vol. vi (1858), pp. 53 — 59.

Parker, W. K., and Jones (see also Jones, T. Rupert) : —
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and Gmelin, vol. iii (1859), p. 474.
Lxxvii. On the Nomenclature of the Foramini/era ; Part II, Walker and Montagu, vol. iv (1859), p. 333.
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(1860), p. 29.
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LXXXa. On the Nomenclature of the Foramini/era; Part VI, AveoUna ; vol. viii, p. 161.
LXXX h. On the Nomenclature of the Foramini/era ; Part VII, Opercidina and Nummidina ; vol. viii, p. 229.

BIBLIOGRAPHICAL REFERENCES. xxi

Lxxxi. Dcsci-iptioii of some Foramiiiit'era iVoiu tlic Coast of Norway; in 'Annals of Natural History,' 2(1 series,
vol. xix (18J7), p. 273.

Pekty, Dr. Max : —
LXXSII. Zur Kenntiiiss kleiiister Lcbensformen in (ler Schweitz. Bern, 1852.

Plancus, Janus : —
Lxxxiii. De Conchis minus notis in Littore Arimiueusi ; Venetia, 1/39 ; 2d edit., Roma, 1"60.

Pritcuard, Andrew: —
Lxxxiv. A History of Infusoria, including the Desmidiaceae and Diatoraaceoe, British and Foreign ; Ith edition,
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Reuss, Aug-Em. : —
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p. 210.
Lxxxvi. Die Foraminiferen und Eiitomostraceen des Kreidemergels von Lemberg ; in ' llaidinger's Katurwiss.

Abhandl.,' Band iv, Wieti, 1850.
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xca. See lxxxviii.
xci. Die Foraminiferen der Westphahschen Krei deform ation ; in ' Sitzungsberichte der kaiserl. Akad. der

Wissensch.' Oct. 20, 1859 ; TTien, 1860.
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der Wissensch.' Bd. xliv; Wien, 1861 ; abstract in 'Annals of Nat. Hist.' 3rdser. vol. viii, p. 190.

Sagra, Bamon de la : —
xcii. Histoire Physique, Politique, ct Naturelle de I'lle de Cuba. Paris, 1839. Foraminifbres par M.
D'Orbigny.

Schneider, Anton : —
xcm. Beitriige zur Naturgescbichte der Infusorien ; in 'Muller's Archiv," 1854, p. 191 ; translated in 'Annals

of Natural History,' 2d series, vol. xiv (1854), p. 321.
xciv. Ueber zwei neue ThalassicoUen von Messina; in ' Muller's Archiv,' 1858, p. 38.

SCHROTER, J. S. : —
xcv. Einleitung in die Konchylien-Kenntniss nach Linne. Halle, 1783-86.

xcvi. Neue Literatur und Beitrage zur Keutniss der Naturgescbichte, sonderlich der Konchylien und der
Steine. Leip:i<j, 1/84-87.

ScHULTZE, Prof. Max. : —
xcvii. Ueber den Organismus der Pohjthalamien {Foraminiferen) nebst Bermerkungen iiber die Uhizopoden im

allgemeinen. Leipziy, 1854.
xcviii. Beobachtungen iiber die Fortpflanzung der Polythalamieu ; in ' Muller's Archiv,' 1856, p. 1G5;
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History,' vol. vii (1861), p. 300.

xxii BIBLIOGRAPHICAL REFERENCES.

SoLDAXi, Am:;. : —
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1780.
CI. Testaccogi'apbia ac Zoophytographia parva et micvoscopica. Siena, 17S9-0f<.

SPEXGtER, Lob. : —
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Verxeuil, Ed. de: —
CIV. On the FnsvKna in the Coal-formation of Ohio ; in ' Silliman's American Jouinal,' 2nd series, vol. ii (181(i),
p. 293.
Walkkr, G. see Boys.

Wallicit, Dr. G. C. :—
CIV a. Notes on the Presence of Animal Life at vast depths in the Ocean; London, ISGl.

cry b. Remarks on some novel Phases of Organic Life, and on the Boring Powers of minute Annelids at great
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(1861), p. .S(iO.

INTRODUCTION TO THE STUDY

FORAMINIFERA.

CHAPTER I.

HISTORICAL SUMMARY.

The group of Animals now generally known under the designation Foraminifera has
only of late received even a small measure of that attention which it is entitled to claim, no
less in virtue of its physiological interest, than on account of its zoological and its geological
importance. It is true that of the minute polythalamous shells of which the group is for the
most part composed, many forms have long been familiar to those Testaceologists who did not
limit their attention to the larger shells of ordinary Mollusks ; but the strong resemblance
which many of them bear to the polythalamous shells of the Nautilm, Ort/ioceras, &c., led to a
general belief that the former belong to animals closely allied in structure to those which pro-
duce the latter. Hence Foraminifera were in the first instance ranked as minute forms oi Nautili;
and although a larger acquaintance with their varied forms, and a more exact appreciation of
the differential characters of these, led to the institution of a considerable number of new
genera for their reception, yet their title to constitute a distinct and peculiar group was not
recognised until the year 1825, when it was pointed out by M. D'Orbigny that, whilst the
larger polythalamous shells have their septa traversed by a continuous tube or siphon, usually
membranous, but sometimes shelly, the chambers of these minuter forms communicate by
s\m^\Q foramina in the septa which divide them — a difference on which he founded his primary
division of the class Cephalopoda into two orders, the Sijjhonifera and the Foraminifera.
Although, as will presently appear, the latter o( these titles was conferred under an entire
misconception of the character of the organisms to which it was applied, yet it has continued
to be that under which they have been since most generally known, none more appropriate
having been yet proposed ; and there can be no doubt that M. D'Orbigny's limitation and
designation of the group has had a most important influence in promoting that more special
study which it has since received, and ofnvhich the results are found to possess an interest and
importance that bear no proportion to the apparent insignificance of the objects which have
^ 1

2 HISTORICAL SUMMARY.

furnished them, but are derived from their bearing on the highest and most recondite
problems of Ph)'siology and of the Pliilosoph}" of Classification.

The history of our knowledge of Foramimfera* may be divided into four periods.

The first inchides all the observations made and published in regard to them, from the
time when they first attracted attention, down to the date when they were grouped together
by D'Orbigny as constituting a distinct type of structure. Among the earlier authors in
whose works notices of them are to be found, it may be well specially to mention Plancus
(lxxxiii), Gualtieri (li), Ledermuller (lxi), Spengler (cii), Gronovius (l), and Schroter
(xcv, xcvi) ; as it was on the figures and descriptions of the first three that Linnaeus founded
the accounts of the fifteen species which he admitted into the twelfth editionf of his ' Systeraa
Naturae' (lxiii), and on those of the last three that Gmelin based the seven additional species
which he added in the edition of the same work (xLViii) published by him in 1788. Nearly
all tliese species, whether straight, curved, or spiral, were ranged under the genus Nautilus ;
one only {Miliola scminulum) of those enumerated by Linnaeus, and another (Z?7Ko/ff nauiiloides)
of those added by Gmelin, having been referred by them to the genus So-pula. It is worthy
of notice that the tendency to variation so strikingly exhibited by the shells of this group w-as
clearly perceived by Linna?us ; who, instead of erecting every well-marked variety into a
separate species (as certain of his followers have done), endeavoured to fi.x upon the most
characteristic variety, and invested it with the appropriate specific name, differentiating
other varieties by some mark, number, or subordinate designation. The descriptions given
by Linnaeus and Gmelin, though sufficient to distinguish the few types to which they apply,
either from each other or from the polythalamous Tcstacea with which they were associated,
would not now serve to distinguish them from the numerous allied forms which have since
become known ; but b\" an examination of the original figures and descriptions given by the
authors from whom those systcmatists derived their information, Messrs. Parker and Rupert
Jones (lxxvi) have succeeded in identifying each of the forms to which they gave specific
designations, and have indicated their characters in accordance with the present state of our
knowledge of the group.

The next important contribution to our knowledge of Foraminifera was made by Messrs.
Boys and Walker, in their work (ix) on the minute shells found in the sand in Sandwich Bay and
its neighbourhood, the descriptions being by Jacob, and the drawings by Walker, from
specimens collected by Boys. An account of this work having been already given in Prof.
Williamson's monograph (ex, Introduction, pp. vi), it will be sufficient here to remark that
(as Messrs. Parker and Rupert Jones have pointed out), amongst the Foraminifera which they

* I have thought it advisahle to limit my historical summary to the most important among the
many coutribntions to our existing knowledge of the group. A far more minute history, iu regard
to NumtnuHtes and their allies, is given hy MM. D'Archiac and Haime in their ' Monographie des
Nummulites' (i). And iu Professor Williamson's 'Recent Foraminifera of Great Britain' (to which
valuable Monograph an excellent Bibliography is appended) special notice is taken of all who have
contributed to our knowledge of this department of the British Fauna.

t " Previous editions," says Professor Williamson, " contained the Polythalamia (' Nautili ')
enumerated by other writers; but in the ninth, Linnscus separates them into species, in the tenth he
gives them specific names, and in the twelfth he attaches to them the synonyms of other authors."

HISTORICAL SUMMARY. 3

enumerated are some fossil types that must have been washed by the action of the sea and
of the streams from the neighbouring tertiary clays and sands, and thus have been mixed with
the recent shells in the mud and sands of the coast. The twenty-two forms which they
characterised as distinct species were for the most part referred by them to the genera
Nautilus and Serjnda ; but it is a curious exemplification of the ignorance then prevailing as
to the true characters of the lower tribes of animals, that Glohigerina bulloides should
actually have been referred by them to the genus Echinus, under the name of E. lohatulus.
All the forms recorded by these authors have been identified by the pains-taking inquiries of
Messrs. Parker and Rupert Jones (lxxvii).

By far tlie most elaborate of all the older contributions to the study of Foraminifera were
contained in the works of Soldani (c, Qi) on the recent and fossil shells of the Mediterranean
and its shores. These works, the product of long-continued and careful research, added very
largely to the knowledge previously existing of the microzoic forms belonging to this group,
of which a vast number (many of them only entitled to rank as varieties) are figured, usually
with such accuracy as to admit of being at once recognised ; but from the Ijinomial nomen-
clature not having been adopted by the author, his materials were not rendered so available
as they might have been to subsequent systematists, and many of the types well figured and
described by him have received a multitude of synonyms at the hands of his successors.

The British Foraminifera soon afterwards underwent a new scrutiny, on the part of a
most able concbologist, Colonel Montagu, who, in his ' Testacea Britannica' and its Supplement
(lxv), enumerated thirty-six species — the chief addition to those of Boys and Walker being
from the Milioline group, several species of which he described under the generic designation
Fermiculum, associating with them under the same designation several species of Lagena and
Entosolenia. It is evident that Montagu was much perplexed by the difliculty of defining
the limits of species in this group ; for in describing his Fermiculum intortum (now known
as one of the varieties of Miliola seminulum) he distinctly states tliat this is so variable in its
formation that without great attention it might be formed into several species. Yet, notwith-
standing the warning he might hence have drawn, he was unable to follow the authors next
to be noticed in their comprehensive grouping of widely divergent varieties ; for when
speaking in his Supplement of the numerous forms of Nautilus [Crist ellaria) calcar delineated
by MM. Fichtel and Moll, he remarks — " If these can be admitted to be the same species, we
may bid defiance to specific definition." The species described by Montagu have all been
identified by Messrs. Parker and Rupert Jones (lxxvii).

Contemporaneously with the first publication of Montagu, a most important treatise by
MM. Fichtel and Moll, specially devoted to the minute Polythalamia (xlv), appeared at
Vienna. This treatise formed but a portion of a much larger work, which would have been
brought out by its authors if they had received sufficient encouragement to do so ; and it
includes only those forms which they ranked under the genus Nautilus. These — unlike the
forms described in the works of Walker and Montagu, which are, for the most part, dwarfed
by their northern habitats — are, generally speaking, large, well-grown specific types, mostly
from the Mediterranean area, but partly also from the Red Sea ; and they are so carefully
described, and so admirably figured, that the work will always remain a valuable standard of
reference in regard to the forms of which it treats. Its authors appear to have been strongly
impressed with the difficulty of defining species in this group, and they revert to the Linnean

4 HISTORICAL SUMMARY.

principle of seizing what appeared to be the most characteristic variety, and distinguishing it
by the specific name, whilst they designate the rest by the addition of Greek letters. In this
manner they differentiated no fewer than twelve varieties of Nautilus {Cristellaria) calcar, five
of Nautilus {Calcarina) Spengleri, five oi Nautilus {Cristellaria) cassis, five oi Nautilus {Nummulina)
lenticularis, three of Nautilus {PeneropHs) planatus. and two of several other species. Still they
were so far trammelled by the notion of the Cephalopodous character of these Polythalamia,
that they did not advance nearly as far in this direction as there now seems good reason for
doing. It was their great merit, however, to have recognised the difficulty which presents
itself whenever large numbers of these forms are brought together, instead of evading it by
selecting their specific types, and then putting aside, as of no account, all which do not con-
form to them, after the manner of certain other systematists. The species described in the
work of Fichtel and Moll have been critically studied with their usual care, and their
present appellations given, by Messrs. Parker and Rupert Jones (lxxviii).

At the same period, Lamarck was engaged in the study of the fossil Foraminifera which
are so abundantly found in the Calcaire Grassier and other Eocene beds of France, especially
in the neighbourhood of Paris. These he described and figured, for the most part, as Cepha-
lopods, but in some instances as Corals, in his series of Memoirs on the Invertebi-ated Animals
found in a fossil state in the vicinity of Paris (LViii); and he subsequently repeated these descrip-
tions and figures in his contribution (lix) to the ' Tableau Encyclopedique et Methodique,' with
others derived from the works of preceding authors, and especially from that of MM. Fichtel
and Moll. In the original edition of his great systematic treatise on Invertebrate animals (lx),
Lamarck repeated his specific descriptions of the foregoing types, with some slight additions,
and he distributed them under generic assemblages, many of which he then first introduced.
Although these new genera were created under a total misapprehension of the true nature of
the group, and were by no means satisfactorily defined, yet many of them (such as Nodosaria,
Cristellaria, Botalia, Nummulites, Polystomella, Orbitolifes, and Orbiculina) were truly natural,
and have been retained in all subsequent classifications. The species enumerated by Lamarck
have been critically examined and identified by Messrs. Parker and Rupert Jones (lxxix).

A very different appreciation of the value of characters was shown by Denys de Montfort,
who introduced into his systematic and illustrated treatise on Conchology (lxvii) descrip-
tions and figures of several of the minute shells now ranked as Foraminifera, stating in his
introduction that he was far from pretending to have given all their genera, but that he
aimed at making some, at least, of their singular forms known to naturalists. To this end he
selected several of the types figured and described by Soldani and by Fichtel and Moll, and
added others from his own collection, distributing the whole according to his own notions.
His delineations of them, however, are of the rudest and most inaccurate character, and his
descriptions are no less erroneous, whilst his systematic arrangement displays the worst form of
the worst school of naturalists, — varieties being erected, not only into species, but even into
genera, upon the slenderest possible basis of difference, and without the least regard to the con-
stancy of the characters assumed for their definition. And thus it has come to pass that out of
about sixty new generic names introduced by De Montfort, only a single one, PeneropHs, has
been adopted by subsequent writers, until I found reason to accept another, Tinoporus, as
having been recognised by him as a distinct generic type, though he entirely misapprehended
its nature. The forms described by De Montfort have been identified and referred to their
proper synonyms by Messrs. Parker and Rupert Jones (lxxx).

HISTORICAL SUMMARY. ^5

It would not be right to pass by the labours of MM. Blainville and Defrance in the
same field. In the articles which they contributed to the ' Dictionnaire des Sciences Natu-
relles ' upon Mollusca and Zoophytes, fossil as well as recent, they gave an account of
several new and important types of Foraminifera, without any correct appreciation, however
of their real nature.

The second period in the history of the group of which we are treating commences
with the presentation to the Academic des Sciences, in 1825, of M. D'Orbigny's systematic
arrangement of the Cephalopoda (lxix), in which he first separated these chambered
shells, under the title of Foraminifera, from the Siphonifera ; still retaining the former,
however, like the latter, as an order of Cephalopods. The entire group of Foraminifera,
as then known to him, consisting of none but multilocular shells, he subdivided into five
orders, according to the geometrical plan on which the segments are successively added.
In the first of these, Stichosiegues, the segments are arranged end to end in a single
line, straight or slightly curved. In the second, Hclicodegues, the segments are in like
manner disposed end to end, but their common axis forms a spiral. In the third, Enal-
lodeyues, the segments are added alternately on the one and on the other side of the
first, along two or even three distinct axes, which may be either straight or curved. In
the fourth, Entomostegues, the segments are arranged on the like alternating plan, but the
double axis forms a spiral, as in the Helicostegues. In the fifth, Agathistegues, the successive
segments cluster one over the other around a central axis, each segment forming half of the
circumference. Each of these orders is subdivided into two families, according as the
growth of the segments is equilateral or inequilateral. And the characters of the genera*
(of which a large number were then first instituted by him) were based in part on the
relation of the segments to one another, but chiefly on the number, form, and situation of the
apertures of the last chamber. To the foregoing orders he subsequently added that of
Monostegues, in which there is but a single chamber, and that of Cgdostegues, in which the
segments are very numerous, and are arranged in concentric circles around that from which
they originate.

No suspicion appears at that time to have crossed the mind of M. D'Orbigny, that the
place of these organisms might be amongst the lowest, instead of among the highest, of the
Invertebrata ; and if his determination of their Molluscous nature was based on any actual
observations of these animals in their living state, it is certain that such observations must
have been of the most superficial character. As his labours have contributed far more than
those of all his predecessors put together, to the extension of our knowledge of the diversified
forms belonging to this group, it was most unfortunate that they should have been com-
menced and carried on under the influence of views regarding the value of characters which
have since been proved to be altogether erroneous.

A correct appreciation of the differences presented by the members of any natural group

* A set of models in plaster of Paris, representing on a large scale the generic and sub-generic
types of these (so-called) microscopic Cephalopods, was issued by M. D'Orbigny about the same time ;
and these have proved very useful in the determination of specimens, whose place in his classification
could not readily be ascertained from his descriptions.

6 HISTORICAL SUMMARY.

can only be based on the careful study of its own plan of organization and of the modifica-
tions wliich this shows itself disposed to undergo ; and cannot be safely deduced by analogy
from the study of any other group, however closely related. Least of all can any analogy
be truly available, which is drawn from one of the highest groups of Invertebrate animals,
and applied to one of the very simplest types of animal structure. Had the inquiries of
M. D'Orbigny been conducted on a more philosophic method, he must have necessarily been
led to the discovery, by the mere comparison of sufficient numbers of individuals, that this
analogy is altogether fallacious, and that the ranjje of variation among Foraminifera is so
much greater than it is in any of the higher tribes of animals, as to render of no account
among the former such differences as in the latter would be of even primary value. But his
practice having been (as I have good authority for stating, and as clearly appears also from
his results) to select, or to cause to be selected, out of any large assemblage of Foraminifera
only the strongly differentiated types, and to leave the intermediate forms altogether out of
view, his dominant misconception was not likely to undergo any modification in the course of
his researches, and we find it still clinging to him even after he had been satisfied that the
true place of this group is among the lowest instead of the highest of the Invertebrate series.
Hence it follows that, notwithstanding the immense value and extent of M. D'Oibigny's
contributions to this department of Zoology, — in the first place by having brought together the
scattered components of the group of Foraminifera, and so differentiated it that it thenceforth
took rank as a special object of zoological and physiological study ; secondly, by having
brought together from all quarters of the globe and from geological deposits of various
periods a vast number of forms previously unknown ; thirdly, by having so far investigated
their characters as to be enabled to group them in generic assemblages, of which a con-
siderable proportion are tolerably natural ; and fourthly, by having furnished a classification
which, although eminently artificial, is still preferable to the chaotic confusion in which they
would have otherwise been left, and which has answered a useful purpose as a provisional
arrangement, — there is scarcely any part of his work which is likely to stand the test of time
and further research. For, as will hereafter appear, a large proportion of his species cannot
be legitimately ranked higher tlian varieties, and many even of his genera must be brought
down to the same level; whilst the basis of his primary and secondary subdivisions of the
group is so unnatural, that it separates under distinct orders not a few types vihich have the
closest mutual affinity, and brings into near approximation others which ought to be no less
widely differentiated. It will be sufficient here to remark that it is now clearly established
that the very same type may develope itself either as a Slichodigue, along a straight or slightly
curved axis, or as a Ilelicoste^ue, along a spiral axis; and that certain of the Cydostegue
order are generically, if not specifically, identical with certain Helicostegues. Some suspicion,
indeed, of the unsoundness of his fundamental assumption that the geometrical plan of hicrease
is a character of primary value, appears to have crossed the mind of M. D'Orbigny ; for he
admits (lxxiii, p. 17) that affinities exist among all the orders, which arise out of a change
in the plan of growth that is liable to occur in many types with the advance of life. This
change he affirms (quite erroneously, as we shall hereafter see) to be always in the direction
of simplification ; — the more complicated or special mode of increase peculiar to the order
giving place to one of a more general character, as where in a Helicosieyuc the spiral extends
itself as a straight line, or in an Enallostegue the alternating arrangement of the segments
gives place to a uniserial direction of increase.

HISTORICAL SUMMARY. 7

The results of M. D'Orbigny's researches on Foraminifera are for the most part recorded
in local Faunas. Thus he furnished to the great work of Ramon de la Saj^ra upon Cuba
(xcii), an important article upon the Foraminifera of that island ; a similar contribution to the
account of the Canary Islands, by MM. Barker-Webb and Berthelot (v) ; and a description
of the Foraminifera of South America to his own travels in that country (lxx). So, in his
' Faune de la Craie blanche de Paris' (lxxi) he described the Foraminifera of that deposit;
and in a subsequent work on the fossil Foraminifera of the Tertiary Basin of Vienna (lxxiii)
he took the opportunity afforded by the extraordinary richness of the collection he thence
obtained thrcutrh Baron Hauer, to give a general conspectus of the entire group as then
known to him, at the same time expressing his entire change of opinion in regard to the nature
of the animal by which the shells of the Foraminifera are formed. His latest views on the
general classification of Foraminifera are contained in his ' Elementary Course of Palseontology
and Geology' (lxxiv), wherein we find a description of all the generic types that occur fossil,
to which the number of such as are only known at the present epoch bears an insignificant
proportion. It is here that we meet for the first time with his order Cychstt'gues, which
includes only four genera ; — Orbifolilcs, previously ranked among corals ; Ci/clolina, instituted
by himself in 18;57, but previously ranked among the lUlicostegues ; with Orbilolina and
'Orbitoides, instituted by himself in 1847, but not previously introduced into his classification.

The iliird period, with which our knowledge of the true nature of the Foraminifera
really commenced, is inagurated by the discovery, first announced by M. Dujardin to the
Academic des Sciences in June, 1835, of the Rhizopod type of structure (xxxiii), which was
followed by the demonstration of the essential identity between the ylmwba and other simple
fresh-water Rhizopods (described by Prof. Ehrenberg among the Polygastric Animalcules) and
the Crisfellaria and similar composite forms of marine Foraminifera which had been previously
ranked among Cephalopod Mollusks (xxxi v). The general results of M. Dujardin's observations
were, that the animal body consists, alike in the naked and in the testaceous Rhizopods, of a
mass o^sarcode, a gelatinous, somewhat granular substance, not enclosed in a distinct membrane,
and capable of extending itself into threads of extreme tenuity ; that there is neither mouth
nor digestive cavity, but that alimentary particles, received into the very substance of the
body, are gradually incorporated with it ; and that both the introduction of these particles
and the movements of locomotion are effected by means of pseudopodial prolongations of the
sarcode, put forth in the testaceous forms through apertures in the shell, and capable, when
retracted again, of coalescing with the general mass. In the case of the composite forms, he con-
sidered the entire animal to be made up of a series of segments which are essentially repetitions
one of another, each possessing an independent vitality of its own (xxxvi). He seems to have
continued for some time, however, in uncertainty as to the extent to which this description of
the animal would be applicable to all the bodies ranked by M. D'Orbigny among the Forami-
nifera ; as we find appended to the names of several of those described by him in the
' Dictionnaire Universelle d'Histoire Naturelle' (as Nonionina, Nummulites, and Rotalia) the
abbreviation 3Ioll. ? as well as Foram.

In the article 'Foraminiferes' cowir\h\xi(ii by M. D'Orbigny in 1844 to the same Dictionary
(lxxit), he altogether abandoned the notion of the Cephalopod affinities of the group (without
giving the least hint that he had ever himself entertained it), and described the structure of

8 HISTORICAL SUMMARY.

the animal in a manner which showed that he accepted M. Dujardin's account of it, though
without tlie least reference to the real discoverer of its Rhizopod character. He assigned to
the group a place among the Radiata of Cuvier, intermediate between the Echinodermata and
the Polypifera, on no other grounds, as it would appear, than a fancied analogy between the
pseudopodia issuing through the pores of the shell and the ambulacral cirrhi of an Asterias,
and between those put forth from the aperture of the last chamber and the oral tentacles of a
Hydra. This account is repeated verbatim in his subsequent work on the ' Fossil Foraminifera
of the Vienna Basin' (lxxiii).

It cannot but seem surprising that, notwithstanding the light thrown upon the
inquiry by M. Dujardin in 1835, Prof. Ehrenberg should in 1838 have announced to the
Berlin Academy his conclusion, professedly based on observations of certain forms of these
animals in their living state, that their true place in the animal kingdom is among the Bryozoa
(xxxix). He described them as possessing a distinct alimentary canal, which extends from
segment to segment ; this, however, instead of being single, as in Nonionina, may (he tells us)
be multiple, as in Geoponus ; so that we must regard each segment of the latter, however
apparently resembling the simple segment of the former, as in reality composed of several
adhering bodies. In one instance (he affirms) he found the mouth surrounded by a plumose
sensory and prehensile apparatus, like that of the Fliistrts and Halcyonella ; but, generall)r
speakmg, he admits that this is altogether wanting, the mouth being a simple aperture. He
saw minute extensile tentacula proceeding from all parts of the sieve-like shell, as described
by Dujardin, and admitted their resemblance to the pseudopodia of Difflitgia, &c. ; but he
remarks, " the rest of their organization, which Dujardin has overlooked, removes them from
the Infusoria quite as far as from a chaotic primitive substance." Besides the alimentary
canal. Prof Ehrenberg described a yellowish-brown granular mass as accompanying and
sometimes surrounding it up to the last of the spirals ; this he considered as an ovary (xl).—
To these views he has lately expressed his continued adhesion (xliv), notwithstanding their
complete inconsistency with the results of all the more recent and trustworthy observations
upon the structure of Foraminifera ; and he has contested those of Prof. Schultze in particular
with an irritation and tenacity difficult to reconcile with the single-minded devotion to truth
which a Naturalist who has rendered such services to science might be expected to manifest.*

Our appreciation of the value of the characters afforded by the form, position, and
multiplication of the apertures of communication between the chambers of the shell, must
obviously differ essentially, according as we suppose these to give passage to an organ of such
fundamental importance as an alimentary canal, or regard them as merely serving for the
connexion of the different segments by stolo?is of sarcode. For variations which in the former
case must be regarded as indicative of such essential differences, both in structure and
function, as would rightly characterise distinct genera or even distinct families, may easily be
admitted on the latter view to be of such comparatively trivial moment as to rank no higher
than specific characters, or perhaps even to be matters of individual difference. As I have
already pointed out, the essential importance of this consideration was altogether disregarded

* The Classification of Foraminifera based by Professor Ehrenberg upon views so erroneous, could
not be expected to replace that whicli was previously in vogue ; and as it is now seldom or never
referred to save as a matter of historical interest, there is no occasion to discuss its demerits in detail.

HISTORICAL SUMMARY. ■»

by M. D'Orbigiiy ; and the influence of his doctrines upon those who interested themselves in
the extension of this department of inquiry was for a long time such, as to prevent any other
progress than that which consisted in the discovery of new forms from time to time, and in
the reference of these to their places in his classification.

It was in the year 1 839 that Prof Ehrenberg announced to the Berlin Academy the remark-
able results which he had obtained from the study of the Chalk formation ; a large proportion
of the material of which he affirmed to consist of the shells, either entire or comminuted, of
Foraminifera ; whilst among the types sufficiently well preserved to admit of being deter-
mined, he showed that as many as ten could be identified with species now existing (xl).

The commencement of that fourth period in which the discovery of M. Dujardin has
received its full recognition, may be regarded as dating from the appearance of two Memoirs
published by Prof. W. C. Williamson (of Manchester) in 1847 and 1848. In the former of
these, which was a Monograph of the genus Lagena (cvi), the important truth was for the first
time formally advanced in regard to this type, that the comparison of a sufficiently large
number of individuals would bring to light such a gradational transition from one supposed
species to another, as to demonstrate that their diS'erences must be accounted as of
individual variation only ; a truth which has since been not only most fully confirmed
by the demonstration of its applicability to the reputed species of every genus of Forami-
nifera that has been worked out with similar completeness, but has been found capable of
extension to many generic and even to some ordinal differences. The latter was a communica-
tion to the Microscopical Society, on the structure of the shell and animal of Polystomdla
crispa (cvii), in which for the first time were given the results of a minute microscopical inves-
tigation of thin transparent sections of the Shells of Foraminifera, and which must conse-
quently be regarded as having furnished the starting-point for all future investigations of a
like kind. Among the facts revealed by this method of research were several that became of
essential value to myself, in the inquiry on whicii I was engaged at the same time in regard
to the structure of Nummulites (xii), and served to confirm the inferences I had deduced
from the other features of that important type, as to its participation in the characters of the
Foraminifera generally. In the course of that inquiry I made the discovery, not only of an
elaborate and previously unsuspected structure in the shell itself, but also of a system of canals,
by which it is traversed, and which seems to have an important function in its nutriti(>n. The
subsequent examination of the minute structure of the shells of numerous recent types by
Prof. Williamson (cvni, cix), Mr. Carter (xvin— xxi), and myself (xiii— xvi), has not only
added greatly to our knowledge of the distribution and purposes of this canal-system, but has
led to a much more correct appreciation than was previously attainable of the value of the
several difi'erential characters presented by the respective types ; and a sound basis has thus
been furnished for a truly natural classification, which cannot, however, be erected otherwise
than provisionally, until the same kind of investigation shall have been carried through a
much wider range of types.

Among the most important of the recent contributions to our knowledge of the organiza-
tion and life-history of the Foraminifera, must unquestionably be ranked the treatise published
by Prof. Max Schultze in 1854 (xcvii). The author has enjoyed the opportunity of studying
several typical forms of the group in their living state, and has most carefully described and

10 HISTORICAL SUMMARY.

most beautifully delineated the remarkable phenomena which they pi'esent. His observations,
which fully confirm and supplement those of M. Dujardin, at present constitute our best
source of knowledge on this part of the subject ; and they have since been extended by further
researches (xcviii,xcix), especially in regard to the Reproductive processes, which still, however,
greatly need elucidation. In his investigations of the structure of the testaceous coverings of
these animals, on the other hand. Prof. Schultze has been less successful, in consequence (as it
would appear) of his want of acquaintance with the best method of preparing thin sections of
them ; and he has consequently fallen into some important errors (such as the denial of the
existence of the canal-system, of which the most perfect demonstration is now afforded by the
examination of the internal casts of these organisms, to be presently noticed), and has failed to
obtain that insight into the real relations of the forms he has studied, which could alone justify
him in proposing a new distribution of the group. Although his Classification is in many
respects an improvement upon that of M. D'Orbigny, yet (as I think I shall hereafter
succeed in showing) it is so far from satisfactory as to leave the way quite open for another
attempt, based upon a more thorough knowledge of the objects to be systematically grouped.
A Classification still more recently proposed by Prof. Bronn (xi) is chiefly founded
upon that of M. D'Orbigny, whilst it adopts certain modifications proposed by Prof Schultze.
It cannot, in my opinion, be regarded as less open to objection than either of the systems for
which it is proposed as a substitute.

An entirely new and most valuable source of information in regard to the organization of
the Foraminifera has recently been afforded by the discovery, first announced by Prof.
Ehrenberg (xLiii) in 1853, that their shells occasionally undergo an infiltration of silicate of
iron, that completely fills, not merely their chambers, but their canal-system, even to its
minutest ramifications ; so that if a shell thus infiltrated should itself undergo decomposition,
a perfect internal cast remains of the original body of the animal, with its extensions through-
out the shell. Of such casts it has been shown by Prof. Ehrenberg that the Green Sands
which present themselves in various geological formations, from the Silurian system upwards,
are in great part composed: and his discovery has thus a twofold value, as, on the one
hand, it places before us far more exact representations of the configuration of the animal body,
and of the connexions of its different parts, than we could obtain even from living specimens
by dissolving away their shells with acid (its several portions being disposed to heap them-
selves together in a mass when they lose the support of the calcareous skeleton) ; whilst it
also enables us to identify with great certainty the types of Foraminifera by which these casts
were originally formed, notwithstanding the entire destruction of their shells. It was soon
afterwards shown by Prof. Bailey (U. S.) that a like process of infiltration is taking place at the
present time over certain parts of the ocean-bottom (iii), and that beautiful internal casts are
obtainable by treating with dilute acid Foraminiferous shells whose cavities have thus filled.
By the application of this method to portions of Mr. Jukes's Australian dredgings, Messrs.
W. K. Parker and T. Rupert Jones have obtained a series of internal casts of most wonderful
beauty and completeness, which I have had the advantage of carefully examining ; and it is
with great satisfaction that I can state that in no instance has this examination afforded any
other result, than that of confirming the conclusions to which I had been previously led by
the study of the shell.

A very different line of inquiry has been recently prosecuted with great success by the

HISTORICAL SUMMARY. 11

same careful and diligent observers— that of the comparison of large numbers of individuals
presenting gradational modifications of the same fundamental types; a method first applied by
Prof. Williamson to La^ena, and afterwards by myself to OrhitoUtes, Orhiculina, Peneroplis,
Opercidina, and Calcarina. The particular results to which they have been thus conducted
will be detailed in their proper place ; at present it will be sufficient to state that they have
been led most fully to accept the views of Prof. Williamson and myself in regard to the wide
range of variation which prevails in the group of Foraminifera generally, and that they have
given to those views a most remarkable development (lxxv — lxxx). The same observers are
engaged upon an extensive comparison of the Foraminiferous Faunas of different localities and
epochs, with a view to elucidate the conditions that determine the prevalence of particular
types. Of this comparison the results already given to the world are replete with interest
(liv, lv, lxxxi).

CHAPTER II.

OF THE RHIZOPODA GENERALLY; THEIR ORGANIZATION AND PHYSIOLOGICAL
HISTORY; AND THEIR DISTRIBUTION INTO SUBORDINATE GROUPS.

1 . Neither the Morphological characters nor the Physiological history of the Foraviinifera,
nor their position in the Animal Kingdom, can be properly understood, without a preliminary
survey of the entire Class of Rhizopoda (of which they constitute by far the most important
section), and an exposition of its most distinctive features as made known by modern
research.

2. The Class of Rhizopoda constitutes, with the Classes of Porifera {Sponges), Infu-
soria, and Gregarinida (to all which it is very intimately related), the Sub-Kingdom which
Zoologists have now agreed to designate by the title PROTOZOA, indicative of the simplicity
of its type of organization, or, as it might be almost said, its deficiency in any definite organi-
zation. In none of its members can any traces be found either of a nervous or of a muscular
system; their digestive apparatus is reduced to its simplest possible condition; of a circulating
system a mere rudiment only can be distinguished ; special organs for respiration and excre-
tion seem altogether wanting ; and although there is reason to believe that true se.xual
products are formed by many of them, yet these develope themselves out of the general
substance of the body, instead of in distinct organs set apart for their evolution. Yet, as will
hereafter appear, these creatures perform all the functions which constitute in their aggregate
the life-history of an Animal. They obtain food either by moving actively in search of it, or
by putting forth prehensile appendages which bring it to them ; they introduce their food
into the interior of their bodies, and subject it to a process of digestion whereby its nutritive
material is extracted from the indigestible residue, which is cast forth by an act of defecation ;
they diffuse this material through the general substance of the body, both by the general
movements of its walls, and by the agency of what seems to be a special contractile organ ;
and they apply it to the augmentation of their own bodies by growth, and to the propagation
of their race by reproductive operations of various kinds.

3. As less differentiation of parts exists among Rhizopoda than in either of the other
classes, and as the beings of which that class is composed may be considered as exhibiting
the distinctive attributes of Animal life in their least specialised condition, its place is obviously
at the bottom of the series. In fact, a state of greater simplification can scarcely be
conceived to exist in any living organism, than that which is presented by the creatures

OF THE RHIZOPODA IN GENERAL. 13

which present the most characteristic types of the group, such, for example, as the
Actinoplirys.

4. The designation of this Class (first conferred by M. Dujardin, xxxiii, in 1835, upon a
portion of the animals now included in it, which he ranked only as a family of Ivfusoria) is
founded upon the power just referred to, which is possessed by all the members of it in a
greater or less degree, of putting forth indefinite extensions of the substance of the body, —
sometimes short, broad, and rounded — sometimes longer, slenderer, and gradually tapering to
a point — sometimes immensely elongated, and narrowed to threads of extreme tenuity, — which
are continually varying both in number, form, and dimensions, and which can be altogether
retracted, so as to become incorporated again with the body-substance. These diverging
processes, termed pseudopodia, are used in some instances merely for the prehension of food ;
in some cases, again, their primary office is to move the body from place to place in search of
aliment ; whilst, in another set of cases, they seem to be subservient to both functions : and
as they bear some resemblance on the one side to the ramifying roots of a tree, on the other
to the feet or locomotive appendages of higher animals, the term Rhizopoda, or "root-footed,"
applied to the class of creatures of which their presence is so distinctive a characteristic, is by
no means unexpressive.

5. The soft and almost homogeneous substance of which the body of these animals is
composed, received from M. Dujardin the designation sarcodc, or rudimentary flesh ; and this
designation may be conveniently used, if it be duly kept in mind that " sarcode " is not a
substance sui generis, but is nothing else than the protoplasm* in which every form of animal
structure has its origin, and from which it is evolved by a process of gradual differentiation.
This substance is composed of an albuminoid base, with oil-particles in a state of very fine
division diffused through it ; it is tenacious, extensible, and contractile ; it is diaphanous,
reflecting light rather more than water but less than oil ; and it is dissolved by alkalies (the
aid of heat being necessary if a weak solution be used), rendered perfectly transparent by
acetic acid, and dyed brown by iodine. In the midst of this substance are usually to be
seen vacuoles, or cavities, containing a thinner fluid, which is often coloured ; these are
extremely variable, both in number and size, and their deficiency in any definite limiting walls
is rendered obvious by their not unfrequent coalescence.f There may generally be observed,
in the bodies of Ithizopods, some differentiation between their central and their peripheral
portion ; the substance of the latter being the more pellucid, consistent, and motile, whilst

* That the " sarcode " of Dujardin is nothing more nor less than animal protoplasm not yet
differentiated into cell-wall and cell-contents — a doctrine which has recently been put forth as new by
Professor Schultze (scix),- — was distinctly stated by the Author iu 1856 (see his Manual entitled 'The
Microscope and its Revelations/ chap. ix).

f These " vacuoles," which commonly form themselves around the particles taken in as food,
were mistaken by Professor Ehrenberg under the influence of his " polygastric " hypothesis, for
multiple stom.ichs, each having its own proper wall, and opening into a common alimentary canal,
■which commences and terminates by a definite orifice. This notion, as will hereafter appear, is alto-
gether ideal, and is utterly inconsistent with the real facts of the case.

14 OF THE RHIZOPODA IN GENERAL.

that of the former contains a much larger proportion of the granules and vacuoles, and seems
less endowed with self-activity, though very easily put into passive motion. This differentia-
tion, which is sometimes scarcely perceptible, in other cases proceeds so far that the coloured,
granular, vacuolated sarcode is surrounded by a perfectly transparent envelope ; and the two
portions thus distinguished may be appropriately designated (after Dr. Strethill Wright) as
the endosarc and the ectosarc.

6. In the cases in which this differentation has proceeded furthest, so that the body of the
Rhizopod bears the strongest resemblance to an ordinary " cell " (as is the case with Amoeba
and its allies (^ 21), a nucleus may be distinctly traced ; in those, on the other hand, in which
the original protoplasmic condition is most completely retained (as seems to be the case with
Gromia, and with the Foraminifera generally), no nucleus can be distinguished. The same
appears to be true of the peculiar contractile vesicle, which may be regarded as a vacuole
with a defined wall ; for this seems to be always present in the " ectosarc " of those Rhizopods
which have that portion of the body most differentiated from the " endosarc," whilst it cannot
be traced in the more homogeneous bodies of such as possess no nucleus. In certain Rhizo-
pods belonging to the former category, the body of each individual contains several nuclei, as
well as several contractile vesicles ; and thus, as Prof. Schultze has pointed out (xcix, pp.
315 — 9), it may be regarded as formed by an aggregation of what would, if still more completely
differentiated, have constituted so many distinct cells. In the highest of these composite
forms (^ 20), indeed, it seems probable that complete cells may be developed in the peri-
pheral portion of the body, whilst its interior retains the condition of homogeneous protoplasm.

7. In a large proportion of Rhizopods the body has the power of forming upon its surface
a firm, testaceous envelope. This, in some instances, appears to be wholly composed of an
organic substance resembling chitine ; but in general it is either siliceous, as in the Folycyslina,
or calcareous, as in the Foramini/era, the mineral constituent in each case being combined
with an organic basis-substance. In certain of the last-named group (^ 60 ) the calcareous
constituent is wanting, and the " test" is composed of foreign particles, so regularly arranged and
cemented together as to give it the shape and general aspect of one formed on the ordinary plan.
The ordinary " tests" of Polycystina and Foraminifera, like the loricce of Diatomacese, must be
regarded as generated by a kind of e.xcretion from the surface of the body ; and although the
elaborate structure of those of the most highly organized Foraminifera might seem, at first
sight, to indicate a less simple origin, yet it will be hereafter shown to be readily explicable
according to that viisw (^ 59). There are Rhizopods, on the other hand, in which the body,
instead of being invested with a sihcified " test," is strengthened by siliceous spicules difi'used
through its substance ; and as there is evidence that in certain cases (^ 18) such spicules are
formed by an excretion-process around pseudopodial prolongations of the sarcode, it is pro-
bable that this is the general fact, more especially as Mr. Bowerbank has shown (viii,p. 282)
tliat the spicules of Sponges have originally a cavity in their interior, which is occupied by
soft animal substance.

8. The subdivision of this Class into Orders seems (in the opinion of the author) to be
most satisfactorily accomplished, by taking as a basis those structural characters which are
most expressive of physiological differences. Such characters are presented in the form,

OF THE RHIZOPODA IN GENERAL. 15

proportions, and general arrangement of the pseudopodial extensions ; for, notwithstanding
their apparently unrestricted polymorphism, it will be found that Rhizopods present three very
distinct types ofpseudopodian conformation, to one or other of whicii they may all be referred,
and that the groups thus formed are eminently natural. How intimately related these diver-
sities are to those fundamental potentialities of each type which find so little structural ex-
pression in this lowest form of animal life, appears from the circumstance that even a particle
of protoplasm detached from the general mass of the body will put forth the pseudopodian
extensions characteristic of its type ; those of the substance forced out by crushino- the " test"
of an Arcella (Plate I, fig. 19), having the broad, lobated form of those of the Amwlja, whilst
those of the substance forced out in like manner by crushing the shell of a Polystomella
(Plate IV, fig. 12) have the delicate, thread-like character of those of the Foraminifera generally.

9. In Actinophrys and its allies (Plate I, figs. 1 — 6), which may be considered as constituting
the central or typical group of Rhizopods, the pseuclopodia are very numerous, and, when fully
extended, are long, slender processes, that gradually taper from base to point, and issue
from the body in a radial direction ; they generally remain distinct when they come into
mutual contact, never undergoing that complete fusion which is common in those of Forami-
nifera; and a slow movement of granules maybe seen to take place along their margin, when
the observation is continued for a sufiBcient length of time under high magnifying powers.
The difi'erentiation between the central and the peripheral portions of the body is such as to
mark out the "endosarc" and the " ectosarc" as, on the whole, distinct from each other,
though no definite line of demarcation can be drawn between them. — With the family
ActinopJiryna, which includes certain forms that possess a firm envelope over a larger or
smaller portion of their surface, there seem to be associated, by their more or less complete
conformity in the foregoing characters, the Acanthometrina, in which the body is supported by
a regular framework of radiating siliceous spicules, the Polycystina, in which it is more or less
completely encased in a siliceous "test," and the Thalassicollina, which, whilst apparently
sometimes simple, are generally composed of aggregations of more or less fully difi"erentiated
cells, supported upon a framework of siliceous spicules. This last family obviously establishes
the transition between the typical Rhizopods and Sponges. The four families now enumerated
seem to constitute an eminently natural order, to which the designation Radiolaria
proposed by Midler,* (lxviii) is very appropriate.

10. In Amwba and its allies, which diverge from the typical Rhizopods in the direction
of Gregarinida and Infusoria (both of which Classes contain forms that are scarcely
distinguishable from it), the pseudopodial expansions are few, short, broad, and rounded (Plate
I, figs. 1.5 — 20), seeming rather like lobate extensions of the body itself, than appendages pro-

* The Rliizopoda Radiolaria of Miiller did uot include the Actinopliryna ; and he separated them
iuto two sub-orders, according as they are Simple or Composite — a di.stinction which does not appear
to the author at, all better founded than that according *to which the Foraminifera are primarilv
divided into Monotlialamous and Pohjtltalamous (see If 52). He is glad to find that the views of
MM. Claparede and Lachmann, on this point, seem to be in accordance with his own ; no notice being
taken, in their classification of Rliizopoda (xxv, p. 434), of the families Spliarozoa and Collospltoercs
established by Miiller for the composite forms of ThalassicolUe.

16 OF THE RHIZOPODA IN GENERAL.

ceedino- from it. They are not put forth equally from any part of the surface, but only from
some particular portion ; and this portion, in some of the testaceous forms, is very narrowly
restricted. They show no tendency to mutual cohesion ; and the smoothness and sharp
definition of tiieir outlines makes it obvious that the surface-layer which they derive from the
" ectosarc " possesses considerable consistence. No movement of granules is to be seen along
their margins ; but the larger pseudopodia receive prolongations from the general cavity of
the body (formed by the vacuolation of the " endosarc"), into which its grantdar liquid contents
freely pass when propelled by the contraction of the " ectosarc." The differentiation between
the " ectosarc'' and the " endosarc" here reaches its maximum ; the former having almost the
solidity of a definite membrane, whilst the particles contained in the latter move so readily
upon one another as to show that its consistence is not even that of a viscous liquid. The
increased tenacity of the " ectosarc" necessarily opposes the free entrance of alimentary
substances through any part of the surface ; and it is pretty certain that in some (at least) of
the Amcebina, possibly in all, there is a special oral aperture. — This group contains
testaceous as well as naked forms, which are all so closely related as to constitute but one
natural order; and for these Rhizopoda the name Lobosa may be suggested, as expressing
the lobe-like character of their pseudopodial extensions.*

11. In i\\Q Foraminifera and their alHes, on the other hand, the characteristic features
of the Rhizopod type are (so to speak) exaggerated. The pseudopodial extensions present no
approach to definiteness, either in shape, size, or number (Plate II, Plate III, figs. 1, 2, 3). Some-
times they appear cylindrical, and sometimes form broad, flat bands ; whilst they are often drawn
into threads of such extreme tenuity as to require a high microscopic power for their discern-
ment; tliey coalesce with each other so readily and completely, that no part of their substance
can be regarded as having more than a viscous consistence; their margins are not defined by
continuous lines, but are broken by the granules irregularly disposed along them, so thai they
appear as if torn ; and these granules, when the animal is in a state of activity, are in con-
tinual movement, passing along the pseudopodia from one extremity to the other, or passing
across the connecting threads from one pseudopodium to another, with considerable rapidity.
In all these particulars they present, as Professor Schultze has pointed out (xcix, p. 314), a
striking analogy to the protoplasmic layer of the interior of certain vegetable cells, such as those
of the hairs of Tradescantia, which exhibit the aspect of an irregular network formed by the
inosculation of threads that spring from the mass immediately surrounding the nucleus, and
very closely resembling that which is formed by the pseudopodial extensions of the body of a
Liehcrkiihnia (Plate II), or a Gromia (Plate III, fig. 2). And as it is along this protoplasmic
network in the interior of the cells of Tradescantia, that the stream of granules moves which
has so long attracted the attention of microscopic observers, there is strong reason to believe
that this movement is due in both instances to the same agency — a sort of peristaltic contrac-

* By MM. Claparede and Laclimann (xxv, p. 43t), the Ammbina and the Actinophryna are
united into one Order, to which they give the name Proteina. The relationship of the latter, how-
ever, to the Acanthometrina, &c., seems to the author so intimate, whilst their differentiation from the
Amcebina appears to him to be so decided, that he cannot hesitate iu the belief that the arrangement
he has here proposed is much the more natural.

OF THE RHIZOPODA IN GENERAL. 17

tion in the threads of protoplasm. The low degree of differentiation in the protoplasmic
substance of these Rhizopods is manifested, not merely in their pseudopodia, but also in the
general mass of their bodies ; for although the external portion is less granular and coloured
than the internal, and is of somewhat firmer consistence, yet there is nothing like a definite
distinction between ectosarc and endosarc, so that the departure from the original homogeneity
of the sarcode is here reduced to its minimum. This low grade of differentiation is marked
also by the absence of the " nucleus" and of the " contractile vesicle," neither of which organs
has been yet detected in any members of this group. By far the larger proportion of the
Rhizopods which agree in these general characters are enclosed in calcareous shells, which
may be either monothalamous or polythalamous ; and such constitute the group of Forami-
nifera. In certain cases, however, the " test" is simply membranous (as in Gromia, Plate III,
fig. 2), or it may even be reduced to the condition of a very transparent film (as in Lieberkuhnia ,
Plate II) ; and such forms are distinguished as Gromida. The physiological condition of all
these beings appears to be so closely accordant, as fully to justify their being combined in a
single Order, to which the name Reticulosa may be given, indicative of the reticulated
character of its pseudopodian extensions. The mode of subdividing this Order will be the
subject of discussion in the next Chapter.

According to the foregoing views, the Rhizopoda may be thus arranged :

RHIZOPODA.

LoBosA. Radiolaria. Reticulosa.

Amabina. Actvnopliryna. Gromida.

/ \ Acanthometrina. Foratiiinifera.

/ \ Folycystina.

Thalassicollina.

INFUSORIA. GREGARINIDA. SPONGIADA.

PROTOPHYTA.

18 OF THE RHIZOPODA IN GENERAL :—RADIOLARIA.

Order RADIOLARIA.

12. Actinophryna.* — Commencing our more detailed consideration of these groups with
the one which may be regarded as the most characteristic type of the entire series, we find a
familiar representative of this in the weW-known Jciinop/uy/s (PI. I, figs. 1 — 4), a not uncommon
inhabitant of collections of fresh water in which aquatic plants are growing, and sometimes
also presenting itself in the sea. The form of its body usually approaches the spherical (fig. 1) ;
but it is liable to modification, on the one hand, from the protrusion of the " contractile
vesicle," v, when turgid, on the other, from the projection either of newly ingested food (fig. 2),
or of particles that are about to be got rid of as indigestible. A still greater departure from
the spherical form is seen when the Jc/i?iop//ri/s is undergoing duplicative subdivision (figs. 3,4).
The average diameter of the body is from l-1300th to l-650th of an inch. From every part
of its surface rndiating pseudopodia e.xtend themselves, usually exceeding in length the diameter
of the body, and tapering gradually from base to apex, but sometimes swelling again at their ex-
tremities into enlargements resembling a pin's head. These pseudopodia, however, vary greatly
both in number and in length ; sometimes they are partially or almost entirely retracted (a
change which may be induced by agitation of the water) ; and they may even disappear
so completely, that the animal cannot be distinguished from an Jniwha until they are
again put forth. The endosarc is distinguished by the presence of granular particles, fre-
quently coloured, which are mostly derived from the matters ingested as food ; and by the
nearer approach of its substance to the consistence of a viscid fluid, as is indicated by the move-
ments of these granules. It also usually contains numerous "vacuoles," some of which are seen
to contain the alimentary matters ingested by the animal, when it is examined soon after feeding.
The ectosarc, on the other hand, is more pellucid and of firmer consistence, though not by
any means attaining to the tenacity of a proper membranous envelope. There is, however,
no definite line of division between the endosarc, and the ectosarc, the one graduating
almost insensibly into the other; but it maybe remarked, that the pseudopodia seem to be
derived from the ectosarc alone, the endosarc not extending itself into them. They
possess, moreover, a degree of consistence which usually prevents them from coalescing when
they come into contact with one another; and whenever such a coalescence does take place, it
is to a much smaller extent than is common among Foraminifera (^^ 32, 33). A circulation of
granules may be seen by attentive observation to take place along the pseudopodia of Acti-
nopliri/s ; but it is far less active than that which constitutes so curious a feature in the life-
history of the Foraminifera (^ 34).

13. Although the existence of a "nucleus" in Jctinoplirj/s has been denied, its presence
(in certain species, at least) must be regarded as a well-established fiict.f It presents itself
as a flattened vesicular body, with a well-defined margin, usually of circular outline, and very

* Ou tbis family, see .xi, xxii, xxiv, xxv, xxvii, xxxvi, xxxvni, lvi, lxxxii, lxxxiv, cii^, cv.
t The term " nucleus " was improperly applied by Kolliker (lvi) to the dark granular sub-
stance which coinmonly occupies the central portion of the body. The existence of a true nucleus was

OF THE RHIZOPODA IN GENERAL :—RADIOLARIA. 19

pellucid ; and its central portion is occupied by an aggregation of granular particles, less
defined at its margin, and less regular in shape. It may be brought into view either by
crushing the body of the animalcule, or by the addition of dilute acetic acid. Its diameter
bears a considerable proportion to that of the entire body, being (according to Stein,)
in A. oculafa almost one-third.

14. The AcHnopliryu seems to have little or no power of moving spontaneously from
place to place; in that respect corresponding with the Foraminifera, but differing (as we shall
see) from Amoeba ; and it obtains its food entirely through the instrumentality of its pseudo-
podia, which, by their peculiar adhesive property, attach themselves to bodies that come into
contact with them. Not only motionless particles of Vegetable matter, but actively-moving
Infusoria, Hotifera, and even small Entoiiiostraca are thus entrapped. When the prey is large
and vigorous enough to struggle to escape from its entanglement, it may usually be observed
that the neighbouring pseudopodia bend over and apply themselves to the captive body, so as
to assist in retaining it, and tliat it is slowly drawn by their joint retraction towards the body
of the Adiiwphrys. In other cases, however, the captive seems as if it were paralysed by the
contact of the pseudopodium, remaining motionless for some seconds, and then, without any
visible movement of its captor, gliding either slowly or rapidly in a centripetal direction
along the margin of the pseudopodium to which it adheres, until it becomes jammed, as it
were, between the base of this and of a neighbouring one. It is usually, in fact, by thus
gliding along the margin of the pseudopodium, as if propelled by an invisible peristaltic con-
traction of its sarcode, rather than by a visible retraction of the pseudopodium, that any
small body not capable of offering active resistance is conveyed to its base. Now and then
it seems as if the appetite of the Aciinnplmjs were sated, or the prey not approved of; for
after a few seconds the movements of the latter feebly recommence, and it glides off the
pseudopodium without any effort on the part of the Adinophrys to retain it. When, on the
other hand, the captive is to be used as food, it becomes invested by an expansion of the pro-
toplasmic substance which the body of the Adinophrys sends forth on either side of that of the
captive, so as to meet and inclose it ; and thus a marked prominence is formed (fig. 2), which
gradually subsides as the food is drawn more completely into the interior. There can be no
doubt whatever that aliment may bo thus ingested at any part of the surface, a new mouth,
so to speak, being extemporized whenever and wherever there is occasion for it. The
struggles of the larger animals, and the ciliary action of Hotifera and Infusoria, may some-
times be observed to continue even after they have been thus received into the body; but
these movements at last cease, and the process of digestion then begins. The body taken-in
as food is received into one of the "vacuoles" of the endosarc, where it lies in the first
instance surrounded by liquid ; and its alimentary portion is gradually converted into an
undistinguishable gelatinous mass, which becomes incorporated with the parenchyma, as
may be seen by the general diffusion of any colouring particles it may contain. Several
vacuoles may be occupied at one time by alimentary morsels ; frequently from four to eight
are seen thus filled, and occasionally ten or twelve. Ehrenberg in one instance counted as

denied by Claparecle in liis earlier memoir upon Adinophrys (xxiv) ; but he has since admitted its
presence, at least in A. Eichornii (xxv, p. 419).

20 OF THE RHIZOPODA IN GENERAL :—RADIOLARIA.

many as sixteen. Whilst the digestive process, which usually occupies some hours, is going
on, a sort of slow circulation takes place in the entire mass of the endosarc, with its in-
cluded vacuoles. If, as often happens, the body taken-in as food possesses some hard
indigestible portion (as the shell of an Entomostracan, or the lorica of a Rotifer), this,
after the digestion of the soft parts, is gradually pushed towards the surface, and at last
escapes by an anal opening in the ectosarc, which extemporises itself for the occasion.
Sometimes it may be seen to glide along a pseudopodiiim from its base towards its apex,
after the manner of an animalcule captured as food, but in a reverse direction.

«

15. When an Adbiophri/s is carefully observed for some little time, a rounded promi-
nence is seen to rise slowly and gradually from a particular point on its surface (fig. 1, a),
sometimes increasing until it attains in small individuals nearly one-third of the bulk of the
entire body, but generally stopping at about one-eighth or one-tenth. The substance of this
prominence is so extremely pellucid that it looks almost like a soap-bubble ; and its margin
is so well defined as to be more clearly distinguishable than that of the body generally.
When it has attained its full size, it suddenly contracts and disappears entirely, so that a
flattening of the outline is often observable at the point previously occupied by this remarkable
elevation ; the margin soon becomes rounded 'again, and gradually rises anew into a projec-
tion, which attains its previous highest development, and then suddenly disappears as before.
This alternation of quick contraction and slow dilatation, which maybe seen to go on with
great regularity for many hours continuously, obviously marks this body to be a "contractile
vesicle," analogous to that of Infusoria ; and it is probable that (as may be clearly made out
in certain forms of that group) the fluid propelled by its contractions is transmitted through
channels in the protoplasma, some of which it distends into " vacuoles," whose contents^
by a slow contraction of the substance in which they are excavated, are subsequently
propelled back into the contractile vesicle. Sometimes the " vacuoles " approach the surface
very closely, and may even form projections from it, so that they have been supposed to be
multiple contractile vesicles. The true contractile vesicle, however, is distinguished by the
constancy of its position, by its sharper outline, and by the rhythmical regularity of its alter-
nating contractions and dilatations.

16. Of the reproduction of Adinophrys so little is at present certainly known, that it will
be preferable to bring the observations which have been made upon it into connection with the
similarly incomplete fragments of this portion of their life-history, which have been attained
by the study of other types of Rhizopod structure (1^ 41, 43).

17. The several genera that rank with Adinnplnys in the family Actinophryna present
its fundamental type of structure under various special modifications. Tiius in Tridiodiscus
the body has the form of a flattened spheroid, and the pseudopodia do not radiate from all
parts of its surface, but form a sort of zone round its equatorial region only. In PlayiopUrys,
again, the origin of the pseudopodia is still more limited, for they all pass off in a bundle from
one and the same part of the body ; and this restriction seems to be related to the investment
of the body at other parts by a definite limiting membrane, which is still, however, very
flexible. In P. cylindrica (Plate I, fig. 6), the body is elongated in form, and the pseudopodia issue

OF THE RHIZOPODA IN GENERAL :—RAmOLARIA. 21

forth from one extremity, which is destitute of any membranous envelope; thus affording a
transition towards such genera as Eughjplia (fig. 5), in which the body is inclosed in a flask-
shaped membranous " test," often elegantly sculptured on its surface, and having a wide
orifice from which the pseudopodia are put forth.

18. ACANTHOMETRINA.* — The siliccous skeletons of the Acatliomeirina, which are all
marine, t consist of a number of elongated spines, which meet in a common centre, and
radiate from this with great regularity (PI. I, fig. 7). These spines arc hollow, and the canal
by which each is traversed opens-out near its base into a furrow, by which a pseudopodian
process of the body of the animal gains access to its interior, to issue forth again at its apex.
There are, however, many pseudopodia not thus inclosed, which strongly resemble those of
Actinophnjs in their appearance and their action. The body is spherical in form, and occu-
pies the spaces left between the bases of the spines, which in some species widen-out so
much as to join each other by their edges at some distance from the centre (fig. 8), thus
dividing the interior of the sphere of sarcode into pyramidal segments. The ectosarc seems
to have a more definitely-membranous consistence than in Aclinoplirys ; but it is pierced bv
the pseudopodia, whose convergence may be traced from without inwards, after passing
through it, and it is itself enveloped in a layer of less tenacious protoplasm resembling that
of which the pseudopodia are composed. The cndosarc contains a number of yellow cell-like
globules, resembling those of Thalassicollm, having a thick peripheral layer and a central
cavity. These are rendered brown by tincture of iodine, and are blackened by the sub-
sequent action of sulphuric acid, whilst the rest of the body assumes a deep yellow colour;
on the other hand, they are turned green by hydrochloric acid.

19. PoLYCYSTiN.\.t — The very numerous group of Pohjcystina, whose skeletons furnish
to the microscopist so many objects of the highest interest for their varied beauty, is also
entirely marine ;§ and is distinguished from the foregoing in having the body itself more or
less completely inclosed in a siliceous envelope, fenestrated or perforated witii numerous

* On tins family, see especially xi, xxv, lxviii.

f The Acanthometra echinoides is described by MM. Claparede and Lachin.inn (sxv, p. 460)
as extremely common on some parts of the cuast of Norway; being brought in abundance by westerly
winds into the fiord of Bergen, from which it disappears when the wind changes; but being always
to be found at Glesnaitholm, which is nearer the open sea. To the naked eye, it presents itself as a
crimson-red point, the diameter of its body (not including the spicules or pseudopodia) being
0'15 roillira., or 0-006 inch. This colour is seen under the microscope to depend upon the pre-
sence, in the central part of the body, of a mass of pigment, which, when viewed by transmitted light,
is no longer crimson, but reddish purple. Acanthomelrie do not seem to have yet been discovered near
our own shores. As they are undoubtedly inhabitants of the North Sea, they should be looked-for on
our eastern coast when the wind blows towards the shore.

I On this family, see especially xi, xxv, xli, xlii, lxviii.

§ They are best known as the " Fossil Infusoria of Barbadoes ;" a large proportion of a Sandstone
that prevails through an extensive district of that island, being composed of the siliceous skeletons
of Polycystina, more or less firmly united together by a calcareous cement.

22 OF THE RHIZOPODA IN GENERAL —RADIOLAUIA.

apertures for the passage of pseudopodia, and often furnished with radiating elongations (fig. 9).
The sarcode body is altogether of an ohve-brown colour, but contains yellow globules, like
those of AcanthometrcB. It does not always entirely fill the shell, especially when this does
not form a complete casing ; as in the Euci/rtidium, only the upper part of whose bell-shaped
" test" is occupied by the body, which is divided into four equal lobes. The pseudopodia of
the Polycystina bear a close resemblance to those of Actinoplirys, alike in their gradually
tapering form, their isolation from each other, their radiating direction, their indisposition to
fusion, and the slow movement of granules along their borders.

20. Thalassicollina.* — Certain forms oiFolycystina, in which the fenestrations of the
siliceous shell are so large and in such close proximity that the solid portion constitutes
nothing more than an open network (as is the case with the Didyosoma of Miiller), serve to
connect that group with the ThalassicoHina. Of these bodies, which are found passively
floating on or near the surface of the ocean, very few forms are yet known, and they are
distinguished by Prof. Miiller into the simple and the composite. Of the former we may take
as an illustration his Thalassicollamorum (PI. I, fig. 12), which seems very closely to resemble an
Adinophry.'i, but presents on its surface, partly imbedded in its ectosarc, a number of composite
siliceous spicules (fig. 13), much resembling those of some species of Tethya. In the Th. nudeata
of Huxley, the dark spheroidal body is described by him as surrounded by a transparent gela-
tinous investment, resembling that which incloses the cells of many Protophytes. The former
consists of a spherical vesicle, 1-G5th of an inch in diameter, the wall of which is formed I)v a
strong, resisting, and elastic membrane, whilst the interior is composed of fluid, holding
in suspension granules of various sizes, with a pale, delicate, nuclear body. In the gelatinous
investment many vacuoles are observable, varying in size from l-62d to l-2500th of an inch,
the smallest being innermost ; and scattered among the vacuoles of the inner portion, imme-
diately surrounding the vesicular body, are many yellow, bright spheres (cells?), about
1-1 600th of an inch in diameter, with a multitude of minute granules. From the surface of
the vesicular body delicate branching fibrils are seen to radiate through the gelatinous
envelope, passing between the vacuoles ; and these are beset with excessively minute dark
granules, which are continually circulating among the fibres, but without any definite direc-
tion. In the complex type, which is represented by the Thalassicolla pundata of Huxley (the
Spharozoum 2}undatum of Miiller), the aggregate mass — which may be either spherical,
spheroidal, or hour-glass shaped — is composed of a number of spheroidal bodies, nearly allied
to the preceding, imbedded (like the cells of a Palmdia) in a common gelatinous investment
(fig. 10). Each spheroid is a cell of from l-200lh to l-250th of an inch in diameter,
having a thin but dense membranous wall, and containing a distinct nucleus surrounded by
a mass of granules (fig. 11); and it is surrounded by a zone of siliceous spicules, each con-
sisting of a short cylinder, from either end of which radiate three or four pointed spines, them-
selves beset with pointed processes, closely resembling the spicules of TlaUdtondria. Round
each of these spheroidal vesicles, moreover, is seen an aggregation of the before-mentioned
small bright yellow spheres ; which are also diffused, though more sparingl)', through the
substance of the common gelatinous investment. And through that substance also there are

* On this family, see especially xi, xxv, lii, lxviii, xciv.

OF THE RHIZOPODA IN GENERAL:— LOBOSvV. 23

seen to extend themselves from the surface of each vesicle (fig. 10) radiating fibres, resembling
those of the simple TlialassicoUa niichata. The central part of the mass is hollowed out by
numcrois vacuoles of considerable size, closely pressed together ; and these sometimes coalesce
into a single cavity, so that the aggregate body (which sometimes attains the diameter of an
inch) is in the condition of a hollow sphere. In another form of the same group, distinguished
by Midler as Collosphcpra Huxlaji, the aggregate body (which seems to correspond in all
essential particulars with the preceding) is included within a clear, transparent, brittle, siliceous
envelope, fenestrated by numerous rounded apertures (fig. 14). In this type (which seems to
approximate to the Fohjcystina) there are no spicules, but each spheroidal vesicle contains a
few prismatic crystals.

Order LOBOSA.

21. Amcebin A.*— Returning now to our starting-point — the most generalized type of
Rhizopods — we find in the Amwha and its allies (some of which are inhabitants of almost
every pond that is tenanted by aquatic plants, whilst others ai'e marine) a condition wliich, as
in some respects transitional towards the Infusoria, has caused Prof. Miiller to distinguish them
as " Infusorial Rhizopods." The body of the Amaha, which may vary in diameter from
l-2800th to I-70th of an inch, cannot be said to possess any definite shape, its outline being
determined by the form and number of its pseudopodian prolongations, which are processes
of the body itself, into which the endosarc often passes as well as the ectosarc, and not merely
extensions of the latter, as in Actinopkrijs. Both in form and number these arc continually
undergoing change ; sometimes they are all retracted, so that the shape of the body is simply
spheroidal (PI. I, figs. 16, 17, a); sometimes it puts forth a few broad, short, lobated expansions
(fig. IG, B, c) ; sometimes these are more numerous, slender, and elongated, assuming a radial
direction (fig. 15, A, B, c, d) ; and occasionally they are so greatly multiplied, radiate with
such regularity, and taper so uniformly from base to apex, as strongly to resemble the pseudo-
podia of Adiiiophri/s (fig. 18). The varieties thus presented have been designated under
different specific names ; but, as MM. Claparede and Lachmann have justly observed, the
grounds of such distinction will appear far from sufficient, when the vemiix\ii&)\e poIi/morpJdsm
characteristic of this type has been duly allowed for.

22. The distinction between the endosarc and the ectosarc is far more clearly
marked in Amoeba than in Adinophrys -, the former being much more fluid, whilst the consistence
of the latter is much firmer. It is through the endosarc alone that those coloured and
granular particles are diffused, on which the hue and opacity of the body depend ; the
ectosarc, which forms a layer of greater or less thickness around it, being perfectly pellucid.
The surface layer of the ectosarc in some forms oi Amoeba (as A. bilimbosa) seems almost to
attain a membranous consistence, a distinct double contour being visible all round the body
when at rest (fig. 17, a). Still, it cannot be said that even in such cases the body is

* On this family, see especially ii, xi, xxii, xxiii, xxv, .xxvir, xxxiii, xxxvi, xxxviii,

LXXXII, LXXXIV, XCIII, XCVII.

24 OF THE RHIZOPODA IN GENERAL:— LOBOSA.

inclosed in a proper membranous envelope ; for this investment seems ready to yield at any
point, so as to give exit to the pseudopodial projections put forth by the softer contractile
ectosarc (fig. 17, b). And in ordinary Amoebce, which have no double contour line (figs. 15,
16), it seems most likely that alimentary and other substances can be introduced through
any part of the ectosarc into the interior, as in AdinopJtrt/s, and that indigestible bodies
can be extruded in like manner, though previously to their escape they may often be seen
to push the ectosarc before them, so as to form considerable projections from the surface of
the body. The central portion of the endosarc seems to have an almost aqueous consistence,
the granular particles diffused through it (which are, for the most part, derived directly from
without) being seen to move very freely upon one another with every change in the shape of
the body. There is not, however, a definite limitation between the wall and the contents of
this cavity ; for the peripheral portion of the endosarc is much more tenacious than the
central, and seems to graduate insensibly into the firmer substance of the ectosarc. In the
typical forms of Amoeba (as A. prhiceps, fig. 16, and A. radiosa, fig. 15), the endosarc
passes into the interior of the pseudopodial extensions. But in A. bilimbosa (fig. 17) and
some otiier forms, in which the differentiation of the endosarc and the ectosarc is unusually
great, these extensions are derived from the latter only. In A. porrecta (fig. 18), on the other
hand, the differentiation is far less complete, and the pseudopodia seem to be as much
formed by tlie endosarc as by the ectosarc; in this and other particulars presenting a link of
transition to the shell-less Reticulosa.

23. A "nucleus" [n, figs. 15, c, 17, a) is always distinctly visible in Amoeba, having,
when most perfectly seen, the aspect of a clear, flattened vesicle surrounding a solid and
usually spherical nucleolus; it is adherent to the inner portion of the ectosarc, and projects
from it into the general cavity. — A " contractile vesicle " seems also to be uniformly present ;
though it does not usually make itself so obvious by its external prominence as it
does in Aclinopltri/s.

24. The more advanced differentiation of the central and peripheral portions of the pro-
toplasmic body of Amoeba is made evident by the effects of reagents. If an A. radiosa
(fig. 15) be treated with a dilute alkaline solution, the granular and molecular endosarc
shrinks together and retreats towards the centre, leaving the radiating extensions
of the ectosarc in the condition of cscal tubes, of which the walls are not soluble, at the
ordinary temperature, either in acetic or mineral acids, or in dilute alkaline solutions, thus
agreeing with the envelope noticed by Cohn as possessed by Paramecium and other ciliated
Infusoria, and with the membrane of ordinary animal cells. The nucleus and nucleolus are
readily soluble in alkalies, whilst they are rendered darker and more distinct by dilute acetic
or sulphuric acid, in consequence of the precipitation of a finely granular substance in the
clear vesicular space that surrounds the nucleolus. When treated with more concentrated
acids, the nucleus and nucleolus first expand and then dissolve.

25. The Amoeba and its allies are distinguished in a very marked manner from all other
Rhizopods by the comparative activity of their locomotion ; instead of remaining fixed to one
spot (except when made to change their place by external agency), and entrapping their food

OF THE RHIZOPODA IN GENERAL :—LOBOSA. 25

by their elongated radiating pseudopodia, tliey are continually moving over the field of the
microscope, and receiving into their bodies any small substances which they may happen to
encounter in their progress. This movement is effected by the protrusion of some part of
the periphery of the body into a pseudopodian process of greater or less elongation : towards
this process, and usually for some way into it, there is a current of the internal granular
substance; at the same time there is a retraction of any processes of the like nature which
might have been previously put forth from the other side of the body, and a reflux of the
granular substance from these towards the centre ; and by a continuance of this change)
the entire Ijody is gradually advanced in the direction of the new extension. The kind
of motion thus executed by an Amaeha is described by most observers as a " rolling" action,
this being certainly the aspect whicii it commonly seems to present ; but it is maintained by
MM. Claparede and Lachmann, as the result of a very careful observation of certain forms
of Amceba that present peculiarities in the disposition of their parts which render them (so to
speak) "test objects" as to this point (such as the A. quadrilineata of Carter, and the A. Umax
of Auerbach), that the appearance of rolling is an optical illusion, for that the nucleus and
contractile vesicle always maintain the same position relatively to the rest of the body, and that
" creeping" or rejjfafion would be a more true description of their mode of movement. On
this view, these animals have their ventral surface constantly differentiated from their dorsal,
it being from the former alone that the pseudopodian extensions proceed ; and thus a tran-
sition would seem to be indicated towards the testaceous Ammhinm, in which the dorsal
surface is invested by a shell, and the pseudopodia are strictly limited to the ventral.

26. When the body of an AiiifEha, or one of its extensions, comes into contact with any
small particle, the movement of the former very commonly presses it against the latter with
sufficient force to cause it to make its way through the ectosarc into the cavity of the
endosarc ;* and thus tlie latter may often be seen to contain Diatomacca, Desmidiacece , frag-
ments of larger Algm, Infusoria, Boti/era, and even Entomostraca, with an occasional
intermixture of inorganic particles. These undergo a kind of circulation in the general
cavity of the interior, which is maintained, as just shown, by the movements of the sur-
rounding contractile substance; and tliis circulation (like the movement of the contents of
the stomach in higher animals) doubtless promotes the digestive process. The larger masses
that are available for nutriment are gradually broken up into finer particles ; and these seem
to constitute the granules which are always to be seen diffused in greater or less abundance
through the liquid interior of the endosarc, the colour of those granules being pretty
obviously the same as that of the matters ingested, and the effects of chemical reagents upon
them being identical. Insoluble bodies appear to be rejected from time to time, by making
their way towards the surface, and then penetrating the ectosarc at the point which happens
to be nearest, just as they are in Adinophrys.

* Whilst admitting that there is uo evidence of the existence of a constant definite oral aperture
iu Ammha, MM. Claparede and Lachmann tliink it conceivable that there may be such an aperture,
of which the lips might be exactly applied to one another, as in Amphileptus, so as only to open at the
moment of deglutition. They express themselves as certain, that in their Podostoma filigerum (^ 28)
such a definite oral aperture exists (xxv, p. 418).

4

26 OF THE RHIZOPODA IN GENERAL :— LOEOSA.

27. Th-e "cohtractile vesicle" does not usually project much from the surface ; though in a
form of ^?K<E^« allied to A.princeps, in which it has been carefully studied by MM. Clapar^de
and Lachmann (xxv, p. 427), it bore a very close resemblance, when in its state of greatest
turgescence, to that of Adino'phrys sol. When fully contracted, it disappeared entirely, but
soon presented itself anew as a minute vesicle in the substance of the ectosarc, which enlarged
little by little until it acquired its original dimensions. On its contraction, from four to eight
vacuoles were seen to project on different parts of the body, often at a considerable distance
from the contractile vesicle ;* and when these had attained a certain dimension they seemed
to put themselves in motion towards it, and to discharge their contents into it, — an operation
which is probably performed by a sort of peristaltic movement along a system of canals
excavated in the sarcode-substance, portions of which are distended into larger cavities by the
contractions of the principal vesicle, and gradually recover their original dimensions by pro-
pelling back to it the fluid which it injected into tliem. This kind of circulation is not
maintained in Amceba with the regularity that is elsewhere seen ; for MM. Claparede and
Lachmann observed that whilst only from half a minute to three minutes sometimes inter-
vened between the contractions, an interval of as much as five minutes might elapse between
the contractions, — a circumstance which shows how necessary it is to watch a Rhizopod for a
sufficiently long time, before coming to a conclusion as to the absence of a contractile vesicle.
It is not likely, however, that the movement of fluid which it seems to be the action of the
contractile vesicle to sustain, is completely suspended during so long an interval ; and as
tlic contractile vesicle was observed to be undergoing a continual change of bulk, it seems
probable that it was executing partial contractions during this period, and M'as refilled in the
intervals of these.

28. A singular modification of the ordinary Amoeban type is described by MM.
Claparede and Lachmann (.xxv, p. 441) under the name Podostoma. This creature (which
was found by M. Lachmann in great abundance at Berlin, in a vessel containing Algae and
Infusoria) may be readily mistaken for an Amwha until it exhibits the appendages which
are peculiar to it ; each of these resembles at its base a short broad pseudopodium, but from
the extremity of this there is put forth an elongated whip-like filament, which is in continual
motion like the jlagellum of certain Infusoria, and which lashes the surrounding water in
every direction. Any foreign particle which may come into contact with this filament is
retained by adhesion to it, and the filament then contracts into a spiral, disappearing at
last in the substance of its pseudopodium, with which it becomes re-incorporated, and
drawing into it the attached particle, which is at first brought to the rounded extremity of
the pseudopodium, is then received into a spoon-shaped depression that forms itself on this,
and then, by a gradual deepening of this depression, finds its way into the interior of the
pseudopodian expansion, and thence into the soft endosarc which constitutes a sort of "general
cavity of the body."

* These distensible vacuoles seem to have been mistaken by some observers for multiple contrac-
tile vesicles ; they have not, however, the well-definecl boundary of tliat organ ; and they do not
undergo the well-marked contractions which it presents at intervals.

OF THE RUIZOPODA IN GENERAL :—LOBOSA.

SI

29. From the simple naked Amceba a transition is presented to those testaceous forms
which accord with it in general structure, by the genus Fseudochhimys, in which the dorsal
surface is protected by a buckler or cai-apace (somewhat resembling the shell (f a FateJJa),
whose substance, however, is not dense enough to prevent its changing its form with that of
the body. In the P. patella described by MM. Claparede and Lachmann (xxv, p. 443), which
is common in ponds in the neighbourhood of Berlin, from six to ten " contractile vesicles" are
seen along its margin, Imt only a single " nucleus" can be distinguished.

30. Of the testaceous Amcebina there are two principal types ; the ArceJltB, which form a
membranous " test," possessing considerable firmness in itself; and the Difflugia, in which
firmness is imparted to the " test" by the adhesion of foreign particles (such as grains of
saud or fragments of shell) to its external surface. Both are inhabitants of fresh water, and
are pretty generally diffused. They have been divided into many species, according to
supposed differences of the most trivial character, which extended observa,tion proves to be
altogether valueless.

31. The "test" oiArcdla is ordinarily of nearly hemispherical form, the circular plane which
closes it in being perforated by a large aperture, from which the pseudopodia are put forth
(PI. I, fig. 19) ; sometimes, however, it is deepened into the form of a vase or pitcher, wliilst
in other instances it is flattened or depressed. Its surface is usually marked with hexagonal

. facets, which are due to the thinning of the membrane at those parts ; and sometimes it
presents a larger pattern formed by bands or depressions passing round it in various directions.
The animal . creeps with the mouth of the shell downwards ; its pseudopodia, which resqmble
those of Amceba, being extended between the flattened side of the shell and the surface over
which it moves. According to MM. Claparede and Lachmann (xxv, p. 444) ; the number of
" contractile vesicles" in ArccUa is very variable, and may increase with the bulk of the animal ;
they are always disposed around the periphery of the hemisphere. Although individuals are
sometimes observed to possess only a single " nucleus," yet this body is generally repeated
several times ; and these multiple nuclei may be seen to form a ring interior to the contractile
vesicles, which they may equal in number, as many as from ten to fifteen having been
observed. The Arcella may be observed to change its " test" many times during the course of
its life, not having any power of enlarging it. When the sarcode-body has become too
bulky for its envelope, it projects from the aperture of the test, from the cavity of which it
almost entirely withdraws itself ; and on the surface of this projecting portion a new test is
formed, which often differs from the old one in those characters which have been considered
to diS'erentiate species. At first, the new test is thin, transparent, and colourless ; but it
gradually becomes thicker, more opaque, and of a light yellowish-brown colour. The old and
the new tests are applied to one another, aperture to aperture (a condition which seems to
have been mistaken for an act of " conjugation") ; and the sarcode-body passes alternately
from one to the other, until at last, when the new test has acquired sufiicient consistence,
the Arcella entirely quits the old one, which very commonly splits under the violence that
seems involved in the final separation (xxv, pp. 44.5, 446). The "test" of Bijjlugia (fig. 20)
is usually more or less of a spherical or ovoidal shape, but is sometimes more elongated into
the form of a pitcher or a flask ; its aperture is generally somewhat notched. When

28 OF THE RHIZOPODA IN GENERAL :— RETICULARIA.

freed from adhering particles, its membranous base is thin, transparent, and colourless ;
sometimes it extends into spine-like processes, by which the test adheres to a fixed point
of attachment. The animal of BiJJlugia appears closely to resemble that of Arcella, but has
not been so carefully studied.

Order RETICULARIA.

32. As each of the preceding Orders contains both naked and testaceous forms, so
do we find that with the proper Foraminifera furnished with calcareous shells, there must
be associated (in virtue of the close conformitj^ in the nature and actions of their
sarcode-bodies) animals which only form a membranous " test," and some even which seem as
destitute of any protective envelope as an Amaba or an Aciinophrys* An example of this last
kind, which afi'ords an admirable illustration of the essential features that distinguish this
group (^ 11), is presented by the Lieberhihnia, a very remarkable Rhizopod, which has been
found in the neighbourhood of Berlin, by MM. Claparede, Lachmann, and Lieberkiikn
(xxv, pp. 464-466). t The body of this animal (PI. II), which measured about l-16th millim.
(l-400th inch) in its longest diameter, was formed of a mass of granular protoplasm not pre-
senting any distinct differentiation of "endosarc" and "ectosarc," and destitute alike of
"nucleus" and "contractile vesicle," but including a large number of "vacuoles" filled with a
homogeneous liquid. From one portion of this mass there issued a sort of stem, from which
all the pseudopodia diverged ; and this stem was enveloped in a transparent sheath, which
might be traced, as a thin pellicle, over the whole surface of the body. From this stem the
granular protoplasm extended itself into branches, whicii ramified with extreme minuteness
and to an extraordinary distance, their length in proportion to the diameter of the body
being nearly three times that which is represented in the plate. Wherever these ramifying
pseudopodia came into contact with each other, the substance underwent a complete fusion
or coalescence ; and thus a network was formed, which might be described as a sort of
animated spider's web, and which was admirably fitted for the acquisition of food. Any
small particles that come into contact with these pseudopodia were held to their surface by
adhesion, and then partook of the general movement of the granules included in the proto-
plasm to be presently described. But when larger bodies were thus entrapped, they became
enclosed in a sort of sheath of protoplasm formed by the blending of the neighbouring
pseudopodia whicli applied themselves to its surface ; and by the progressive contraction of
this they were drawn towards the body, as in the Adinoplinjs (1 14). In one instance a large
Stentor thus captured was seen to make its escape, carrying with it a portion of the pseudo-
podial expansion of the Lieherhiihiia. The granules so abundantly distributed through the pro-
toplasm of the body and its extensions were obviously for the most part of external origin ;
many of them being particles of chlorophyll derived from vegetable organisms that had been

* On this group see especially iv, xxv, x.xxiii, xxxv, xxxvr, lxxxiv, xcvii.

t The animal described by Professor Bailey (iv) under the name of Pamphagus mulabilis seems to
have been nearly allied to this, if not identical with it.

OF THE RHIZOPODA IN GENERAL :—RETICULARIA. 29

taken-in as food, whilst the introduction of others, that happened to he on the surface of the glass,
took place under actual observation. These granules were in a state of continual movement,
passing from the interior of the body and along the stem and branches of the pseudopodial
expansions towards the extremities of these, and then back again into the interior of the
body, in the manner that will be more particularly described in Gromia. The current was
rapid, and seemed to attain its maximum of intensity at the surface of the pseudopodia. It
was noticed in this interesting animal, which was kept for several days under observation,
that the pseudopodia were always most expanded in the absence of light, being splendidly
displayed when the slip of glass was first brought out of darkness and placed upon the stage
of the microscope ; but that after a few moments they began to retract themselves, their
viscid substance flowing rapidly towards the body with a wave-like motion ; and in a short
time it became impossible to recognise a Rhizopod in the dark motionless mass beneath the
microscope.

33. In the Gromia, some forms of which inhabit fresh water, whilst others are marine,
the sarcode-body, which is of essentially the same character with that of Lieherkiihnia, is
enclosed in a yellowish-brown membranous " test " of ovoidal shape, with a single round
orifice of moderate size, through which the protoplasmic substance extends itself from the
interior through the surrounding medium (PI. Ill, fig. 2). When the animal is in a state of
rest, the whole of this is drawn within the test; and when its activity recommences, single
fine processes are first put forth, which move about in a sort of groping manner until they
find some surface to which they may attach themselves. When this attachment has taken
place, new sarcode flows irtto them, so that they speedily increase in size ; and they then
elongate themselves by sendit^g out finer ramifying processes, which, in diverging from each
other, come into contact with' those proceeding from other stems, and, by mutual fusion, form
a set of inosculations or connecting bridges between the different systems of ramifications, so
that the whole becomes a complicated network extending to a distance of six or eight times
the length of the body. This network continues to undergo incessant changes, new filaments
being put forth in diff'erent directions, sometimes from its margin, sometimes from the midst
of its ramifications, whilst others are retracted. Not unfrequently it happens that at a spot
where two or more filaments meet and fuse together, a lamina is formed by an expansion of
the viscous protoplasm that flows towards this point; and from such an expansion a new set
of thread-like processes is given off", as from the central body, of which several examples are
shown in the figure. It is not only, however, in the protoplasmic substance directly as it
issues from the mouth that the pseudopodia originate ; for this substance is seen to
extend itself over the surface of the test, and may put forth pseudopodia from any part of it.
The greater development of these at the posterior extremity of the shell would seem
to indicate that they are employed for fixing it, and thereby cnaljling the animal to put
forth more power when seizing and drawing into itself as food living creatures that can
struggle against its ensnaring action. (The greater part of the Foraminifera are firmly fixed
by the adhesion of their shells to the surfaces of Algse, Zoophytes, Mollusks, &c.) Any minute
particle which may chance to come into contact with a pseudopodium, and which is retained
in adhesion to its viscid surface, soon becomes imbedded in its protoplasm, and is subjected
to the general movement to be presently described. But when a larger body is thus

30 OF THE lllIIZOPODA IN GENERAL :—RETICULARIA.

entrapped, a number of pseudopodia apply themselves to its surface, and a sort of flux of
their viscid protoplasm takes place towards it, until it becomes ensheathed with this
substance, as shown in the case of the Diatom entangled amongst the pseudopodia on the
right side of the figure. A reflux of the protoplasm of the pseudopodia then takes place, and
the body entrapped by them is gradually received into the mass of sarcode lying outside the
mouth of the test, through which it passes into its interior if not too large to find
admission. The lorica of Diatoms, portions of Confervm, and other similar bodies, bearing a
considerable proportion in length to the whole diameter of the test, may often be distin-
guished in its interior, as shown in fig. 2. — As the form of the test of Gromia does not
admit of any addition being made to its capacity, so as to accommodate it to the growth of
the contained body, it appears probable that the latter (like Arcella, "f 31) quits it, and forms
a new test whenever it has outgrown the old one ; and it does not seem unlikely that an
accumulation of indigestible substances may be got rid of at the same time, as the enclosure
of the body in a firm envelope must prevent these from being ejected from time to time
through an extemporised anus, with the facility which we have seen to characterise the
process of defecation in the naked Rhizopods.

34. Through tlie whole of tlie protoplasmic network, a movement of granules is con-
tinually taking place, chiefly in two directions — from the bod)' towards the extremities of the
pseudopodia, and from these extremities back to the body again. This movement may be
seen in every one of the processes ; but it is only in the broader filaments containing
numerous granules, that two streams can be seen passing at the same time in opposite
directions. In the finest filaments, whose diameter is less than that of the granules, the
latter glide along their surface at distant intervals, each passing up as far as the termination
of the filament, and then returning, sometimes meeting and carrying back with it a granule
advancing in the opposite direction. Even in the broader processes, granules are sometimes
observed to come to a stand, to oscillate for a time, and then to take a retrograde course, as
if they had been entangled in the opposing current — just as is often to be seen in Ckara.
When a granule arrives at a point where a filament bifurcates, it is often arrested for a time
until drawn into one or the other current ; and when carried across one of the bridge-like
connections into a difi'erent band, it not unfrequently meets a current proceeding in the
opposite direction, and is thus carried back to the body without having proceeded very far
from it. This curious circulation, as already pointed out (f 11), so nearly resembles the
cyclosis that takes place within the cells of PJant.s, as to leave no reasonable doubt that the
conditions of the two sets of phenomena are essentially the same.

35. In one large section of the Foraminifera, of which Miliola may be taken as the type,
the calcareous "shell," whether monothalamous or polythalamous, is formed upon the same
plan as the "test" of Gromia ;* the wall of each chamber being perforated by no other openings

* Althougli the author lias here followed the example of other Systematists in separating Gromia
and its naked allies from the true Foraminifera, he is by no means certain that such separation, h(?wever
convenient in practice, is scientifically justifiable ; since the difference in the coinpositiou between the
membranous "test" of Gromia and the calcareous "shell" of Miliola scarcely seems to him a character

OF THE RIIIZOPODA IN GENERAL :—RETICULARlA. 31

than those which communicate with tlie adjacent chambers, and the last-formed chambers
having only a single orifice* of communication with the exterior, from which alone pseudopodia
are put forth (PL III, fig. 3). But all these openings are usually so free, that no obstacle can
exist to a transmission of nutrient materials obtained by the pseudopodia put forth on the
exterior, to the segments of sarcode-body that are furthest removed by it, by a circulation of
granules through the entire mass analogous to that which has just been described ; and thus
the physiological condition of the animal of Miliola and its allies may be considered to be in
all essential respects the same as it is in Gromia. This will still be the case, even when the
number of such segments is immensely multiplied by the subdivision of the principal sections,
as in the animal of Orbitolites (PI. IV, fig. 14), Orbiculina, and Alveolina ; and the evidence
which the author has been fortunate enough to obtain in regard to the first of these types is
sufficient to show that there is no indication of deficient vitality in the portion of the sarcode
body which occupies the centre of the largest disk, the character of its substance being
precisely the same throughout.

36. A very different condition presents itself, however, with the two great groups
(together constituting by far the largest proportion of the entire series), of whicii Rotalia and
Operculina may be regarded as the types. For in these tiie apertures in the septal planes by
which the chambers communicate with each other, and by which the special communication
is established between the last chamber and the exterior, are so much narrowed that they
are sometimes not easy to be discovered ; but, on the other hand, the lateral walls of the
chambers are everywhere perforated, more or less closely, with pores for the exit of pseudo-
podia. Hence when a living Rotalia is under observation, its pseudopodia are seen to extend
themselves from every part of its surface (Plate III, fig. 1), and not to proceed only from the
orifice of the last chamber, as in IlUiola. When the pseudopodia have been entirely retracted,
however, it is generally observable that those first put forth proceed from the orifice (or
orifices) of the septal plane of the last chamber; and frequently a considerable time elapses
before the pores of the lateral walls give exit to protoplasmic filaments. , Often, again, these
filaments are put forth only from the two or three last-formed chambers. Still, when such an
animal has remained long undisturbed, its pseudopodia may be seen to extend themselves
from all the pores on its surface. If these are used for the introduction of alimentary
materials into the body, it is obvious that such materials only can thus enter, as are in a state
of sufficiently fine division to pass through these pores. No difficulty need be felt on this score
in the case of the Rotaline group, in which the diameter of the pores, being commonly as
much as 1 -3000th of an inch, allows the passage of pseudopodia of by no means the smallest

of sufficient importance to differentiate groups which are so intimately allied in their general physiological
conditions, especially when it is borne in mind that some of the Milolida form their shells, after the
manner of Difflugia, by the agglomeration of particles derived from without, instead of by an e.xudation
from within. Moreover, if Gromia be regarded as the monothalamous type of the Milioline series, it
naturally fills a place exactly parallel in rank to that of OrbuUna in the Rotaline.

* The single large mouth is sometimes replaced, as in Peneroplis and Orbitolites, by a series of
pores ; but these, being limited to the " septal plane," have no relation whatever to those which allow
the passage of pseudopodia through the lateral walls of the chambers of Rotalia and Oiierculina.

32 OF THE RHIZOPODA IN GENERAL:— RETICULARIA.

size. But in the Operculine the diameter of the pores is so much smaller, — being commonly
no more than 1-1 0,000th of an inch, and often less, — that only the very finest pseudopodian
threads can issue from them, and only the minutest granules can be received into them.
Certain facts in the structure of the shell, to be hereafter detailed (Chap. II), render it almost
certain that the protoplasmic substance extends itself at certain times, if not constantly, over
the whole exterior of the shell, as in Gromia (^ 33) ; and hence it is by no means impossible
that the digestive process may really be performed in this external layer, so that only the
products of digestion may have to pass into the portion of the sarcode-body occupying the
cavity of the shell.

37. The sarcode-body of such Foramini/era as have been observed in the living state, is
observed to be more or less deeply coloured ; its tint being in some instances a yellowish-
brown, in other cases a crimson-red. This colour seems in some instances to be uniformly
diffused through the whole mass of the sarcode, probably owing to the fine state of division
of the particles which possess it ; but in the larger forms it occurs in much larger and more
scattered masses, which appear sometimes to be collections of granules, and in other
cases to be vacuoles filled with a coloured liquid. In the polythalamous Foramini/era it is
nearly always to be observed that the colour is deepest in the segments of the body which
occupy the oldest chambers, and that it fades progressively in the segments which intervene
between these and the one that occupies the last-formed chamber, which is often nearly colour-
less. There is strong reason to believe that the colouring material is directly derived from
external sources, thougli modified in some cases by the agency of tlie animal itself. It was
found by Schultze, that he could increase the intensity of the colour, and cause even the
last-formed segment to be dyed with it, by feeding the animals with substances fitted to
impart it ; whilst, on the other hand, by depriving them of food that would furnish colour,
he could reduce the older segments to almost the same state of deficiency in this respect as is
usually presented by the last segment alone. It is stated by Schultze that the colouring
matter of Foramini/era, when treated with dilute sulphuric or hydrochloric acid, is changed
to an intense verdigris green ; and by dilute nitric acid, first to green and then to yellow.
Concentrated sulphuric acid destroys the colouring substance, but when combined with sugar
renders it green. By concentrated solutions of potass and soda, the coloured granules are
dissipated without change ; and in ether and alcohol they are readily and completely
dissolved. In these reactions the colouring matter agrees with that of the Dialomacece, from
which tribe the greatest part of the food of the Foramini/era is probably derived.

REPRODUCTION OF RIIIZOPODA.

38. So little is at present known of the manner in which Rhizopods belonging to any of
the foregoing types propagate their kind, that it seems preferable to bring together
the principal facts hitherto recorded respecting the mode of reproduction in all these
groups ; more especially as they will be found to bear a very close resemblance to one
another.

39. The deficiency of structural differentiation, either morphological or histological, which

UEPROUUCTION OF IIHIZOPODA. 33

is so remarkable a characteristic of this group, would lead us to infer that, as every part of the
homogeneous sarcode seems possessed of the same attributes in regard to the pliysiological
activity of the individual, so it should be equally able to participate in that modification of
the ordinary processes of nutrition wliicii gives origin to new and independent beings by
continuous growth. There is evidence that this is actually the case ; for not only do portions
of the sarcode-body detached from the principal mass forthwith comport themselves after the
manner of that from which they have been separated, — the sarcode forced out by crushing
the shell of a living Arcella, for example, putting forth lobose extensions on the Amoeban type,
whilst that forced out by crushing the shell of a living Poh/.^foiJi<'lla puts forth the slender
branching pseudopodia of the Reticularian (Plate I, fig. 12), — but there is every reason to
believe that such detached portions can continue to maintain an independent existence. Thus
it is not unfrequcntly seen in AiiKcba that when a pseudopodial process or lobe of the body
has been put forth to a considerable length, and has become enlarged and fixed at its
extremity, the subsequent contraction of the connecting portion, instead of either drawing the
body towards the fixed point, or retracting the pseudopodial lobe into the body, causes the
connecting band itself to become more and more attenuated until it gives way, leaving the
terminal enlargement altogether detached ; and this portion speedily shoots out pseudopodial
processes of its own, and behaves itself in all respects as an independent Amce.ba. Still more
satisfactory evidence to the same effect has been obtained by myself in my detailed study of
Orbitolites ; for not only have I met with numerous specimens in which the loss of any portion
of the disk was repaired by a new growth taking place in every respect upon the regular type
(Plate IV, fig. 2(i), but I have been fortunate enough to obtain a specimen (fig. 27) in which
a new disk has been formed from what was obviously nothing else than a fragment broken
away from the margin of a much larger one. — Since, therefore, in the more as in the less
specialised types of Rhizopod conformation, any portion of the sarcode-body can thus
comport itself as an independent organism, it may be reasonably inferred that this is true
of the entire group, and that the detachment of such portions, after the manner of the
gemmation of higher plants and animals, is one mode in which Rhizopods are ordinarily
multiplied. And such would seem to be the most probable explanation of the appearances
seen by Schneider (xciii) in Dijliii/ut ; which indicate that a whole colony may be formed
by gemmation from the pseudopodial lobe of one individual.

40. Inferential evidence to this effect is abundantly afforded by the study of the polytha-
lamous types of Foramiiiifera ; for in every case in which it has been hitherto possible to
examine the sareode-body of these animals, its character has been found to be uniformly the
same throughout, every segment precisely repeating every other, save in the difference of
colour already noticed, and in certain appearances occasionally presented by the outer
segments (^ 48), which are probably indicative of a more special kind of reproductive action.
The entire sarcode-body of an Orbitolites (Plate IV, fig. 14), for example, is made up of an
aggregation of segments that have been successively put forth, by a process essentially
resembling gemmation, from the primordial segment which continues to occupy the central
chamber; and it affords one of the best examples which the Animal Kingdom can present, of
that " vegetative'' or " irrelative" repetition which is an essential feature of all low grades of
organization. Every one of these segments, there is strong reason to believe, could maintain

5

34 OF THE RHIZOPODA IN GENERAL.

an independent existence ; and yet so long as it remains in connection with the rest, it shares
a common life with them, the nutrient materials being introduced in the first instance through
the marginal segments, and being transmitted by protoplasmic circulation (ft 32 — 34) through
the entire mass. But in a large proportion of the polythalamous Foramiiiifera, the segments
thus successively formed are much more completely isolated from each other than are
those of OrUtolites ,• and there are several in which the chambers of the shell that
envelope these segments have so little connection with those that precede and follow
them, as to be easily detached from them and from each other. This is the case, for example,
with GlohigmiKc, and with many of the Nodosaria> ; and there is reason to believe that the
separation of their parts, which can be produced by very slight external violence, ma)'
be a means of their nudtiplication and diffusion.

41. Besides this, which may be considered the mofst general method of reproduction
among Rhizopoda; other more special forms of that process are' indicated by observed facts.
In those types which exhibit, in the differentiation of "ectosarc" and " endosarc," and in the
presence of a nucleus, the nearest approach to the condition of cells, multiplication takes place,
as in growing cells generally, by a process of binary subdivision. This may often be witnessed
in ActinopJiri/s, round whose spherical body an annular constriction forms itself, which
gradually deepens so as to separate its two halves by a sort of hour-glass contraction
(Plate I, fig. 4) ; and the connecting band becomes more and more slender (fig. S), until a
complete separation of the two halves occurs. The process of fission, which may be completed
within half an hour from its commencement, seems to take place first in the contractile vesicle;
for each segment very early shows itself to be provided with its own (Fig. 4, v, v), and the
two vesicles are commonly removed to a considerable distance from one another. The
segments thus divided are not always equal, and sometimes their difference in size is veiy
considerable. — The like process of duplicative subdivision has been witnessed also in Amceba.
Whether in either case this subdivision commences in the nucleus, or extends through it
subsequently, has not yet been ascertained.

42. It is affirmed by Schneider (xciii n) that Amccba sometimes passes into an encysted
condition. He observed it first to become globulai', and then to form a firm membrane on one
side, whilst the other portion maintained its peculiar character and actions. (In this state it seems
to have resembled the A. bilimbosa of Auerbach, Plate I, fig. 1 7.) By degrees the membi-ane
extended itself over the whole body, the moveable portion constantly becoming smaller, until
at last a completely closed cyst was produced, in the clear interior of which a round nucleus,
with a reddish halo, exactly like that of Polytoma and other Monadina, might be distinctly
observed. To what this encysting stage leads, there is at present nothing to show. — A
change which seems to be of the same nature has also been observed b)^ Schneider (xciii)
in BiJJfiif/ia, and by Schidtze (xcvii, p. 25) in Lagynis Baltica (Plate I, fig. 21, b).

43. On the other hand, a junction of two individuals has been seen to take place in
Adinophrp, which has been supposed to correspond with the " conjugation '" of certain
Protophytes. It is very doubtful, however, if this junction or "zygosis " involves a complete
fusion of the substance of the bodies which take part in it; and there is not sufficient evidence

RKPRODUC'J'ION OF RHIZOPODA. Sf)

that it has any relation to the act of reproduction. Certain it is that such a ''zygosis" may
occur, not between two only, but between several individuals at once, their number being
recognised by that of their contractile vesicles ; and that after remaining thus coherent for
several hours, they may separate again without having undergone any discoverable change.
Whether, by any process of a sexual character, germs are developed within the body, and
are then set free, must at present be regarded as quite uncertain ; the only reliable evidence
on this point being that which is afforded by the observation of Professor KiJlliker, that very
small individuals oi Jcfi//op/tr//s sometimes present themselves, measuring no more than -01 or
"02 millim. (l-2560th or l-12S0th incli), and presenting very few and inconspicuous granules.
But these may be gemmae or small segments separated by the process of subdivision, and not
sexual products. And it must for the present be held to be quite uncertain, whether the
body wliicli we know as Aciinoplirijs does not go through some entirely different phase, before
the completion of its life-history. — A like process of conjugation has been seen to take place
also in several AinmhiiKE, testaceous as well as naked ; and the same doubt exists whether
this " conjugation '' has any import at all corresponding to that of sexual union among the
higher animals, and whether the being which is known as Amceba is anything more than one
form of an organism, whicli would present itself to us under other very diverse aspects if the
whole of its life-history were known to us.*

44. Certain appearances, however, have been obsei-ved by Mr. H. J. Carter (xxii,
pp. 223-233) among Amahina and Actinophnjna, which may be provisionally accepted as
indicating that true sexual products are formed in the interior of their bodies, and arc after-
wards set free by their disintegration. In Amaba the formation of the male apparatus appears
to commence by an increase of size in the vesicular portion of the nucleus, which also becomes
more or less globular (Plate IV, fig. 6, a) ; and its contained aggregation of granules then aug-
ments so as to occupy a third of the interior of the animalcule, and undergoes successive
binary subdivisions, by which it is broken up into numerous segments. These segments
assume a circular compressed or globular form, and continue entire until the granules
(spermatozoids ?) of which they are composed become fully developed, when the latter
acquire the power of locomotion, and then separate from each other, the original containing
vesicle in the meanwhile disappearing. In this way some individuals out of a group of
Amceba radiosa bearing such granules were seen moving about, even when so reduced that
hardly anything but their external pellicle and the one or two spherical segments of the
granulated nucleus that remained in their interior were left. Sometimes these segments
are evidently held together by a soft mucous envelope, which, being polymorphic, assumes
the form of Actimphriis (fig. 7), and exhibits locomotive power ; while in other instances tliis
capsule becomes firm, transparent, and spherical ; and the granules do not leave it until
they become endowed with independent activity. When the latter is the case, the sperma-

* The Author considers that it would be foreigu to tlic purpose of the present work, were lie here to
entur upon a discussion of the curious observations of Hartig, Carter, and others, who maintain tliat
Amceba and Actinophrijs, or organisms undistinguishable from them, are formed as individualised seg-
ments of protoplasm within Vegetable cells, entering upon their independent Animal life when set free
from these.

36 OF THE RHIZOPODA IN GENERAL.

tozoids (?) may be seen, if fully developed, to be bounding about in the interior of their
capsules, while the capsules themselves are still rolled on in the sarcode of the Amcebn under
progression. At other times, the whole mass of the spermatozoids (?), all separated and freed
from their capsules, mav be seen to be diffused through the body of the Aniceba whilst still
in active polymorphism and locomotion. Lastly, the parent sometimes dies in this state ; and
then the mass of spermatozoids (?) may be seen to undergo gradual disintegration, as the
granules, by twos or threes or more, disentangle themselves from the sarcode, and bound off
into their new element. — The development of granvdar spermatozoids (?) has been observed
by Mr. Carter to take place after almost exactly the same fashion in Eiif/Ji//jha aheoUdu (fig. 9), in
which their diameter averages from l-16,000th to l-12,000th of an inch; and similar bodies
have been seen bv Schneider (xcin) to develope themselves from the nucleus of Diff!(i(/ia.

45. Again, not only Amxeha, but Eitt/l^/pIi(V, Diffliif/ice, and ArcdUna, have been frequently
observed by Mr. Carter to contain in the midst of their sarcode a number of discoid or
globular bodies having the appearance of ova (Plate IV, figs. 8, 10, 11). At an early stage
of their formation each of these bodies consists of a transparent capside, lined with a faint-
yellow film of semitransparent matter, which, subsequently becoming more opaque and
yellowish, also becomes more marginated and distinct.* They are very commonly accompanied
by active molecular granules. Their number is sometimes so great, that, as in the specimen of
Amoeba verracoHa represented in fig. 8, the entire body comes to resemble an ovisac filled
Avith granuliferous germ-cells. In Euglypha alccolala they are first seen, to the number of
from four to fifty, congregated round the nuclear vesicle, though afterwards they become
diffused through the sarcode-body generally (fig. 10) : their diameter averages from 1 -4000th
to 1 -3000th of an inch, or something less than that of a human blood-corpuscle.

46. Although the development of spermatozoids (?), and of ovules (?) takes place more
profusely in distinct individuals than in the same, yet it is by no means uncommon to see
individuals of Em/Iyplia akeolata containing both kinds of bodies (fig. 11) : there is no such
gradation between them, however, either in size or aspect, as would suggest the inference
that the one form originates from the other.

47. Of the subsequent history of these bodies very little has been yet ascertained, and it
cannot be stated with any approach to probability in what way their development and actions
are related to the " conjugation" already mentioned as not unfrequcntly to be seen between two
or more Amoebina or Actiiiopliri/na. It is stated by Mr. Carter that the granular spermatozoid (?)
development does not take place until after conjugation ; and that after Enr/h/plice have united
themselves, not only in pairs but triply and quadruply, it is common to see only ovules
developed in all the individuals of one group, and spermatozoids in those of another.
In Euglijijhcp (fig. 11) which contained both ovules (?) and spermatozoids (?), the former were
often observed to be surrounded by actively-moving swarms of the latter ; and the same is

* The "seed-like bodies" of Spongillu Lave been found by Mr. Carter to contnin numerous
transparent, globular sacs, each of which includes a greater Or less number of ovules f>) resembluii,'
those described above. Thus, each of these sacs may be cousideied as the representative of an Amoeba.

REPRODUCTION OF RHIZOPODA. 37

also observable in Sponfjilla, in which Mr. Carter thinks that he has seen the incorporation of
one of the spermatozoids (?) with an ovule (?), in a manner that indicates the act to be one of
fecundation. He has been able to watch the ovules from their first appearance until they
acquire the aspect of simple Rhizopods with a power of putting forth pscudopodia ; and he
believes that when they have attained this condition they are set free by the death of the
parent, and, escaping from the cavity of its test, soon form new tests for themselves. By his
subsequent observations upon Am(eha verrucosa (xxiii, p. 37), Mr. Carter was led to believe
that each ovule in that species gives origin to a number of independent " polymorphic" cells,
resembling those which he had previously described as constituting the first product of the
ovum of Spont/illfi : and that these pass several months in their immature condition, before
taking-on the characteristic aspect of the parent.

48. Of the special modes in which Reproduction is effected in Foraminifera, scarcely
anything is yet known. It was observed by Dujardin that the protoplasmic contents of the
chambers of Tnmratulina sometimes group themselves together as spherical masses ; and I
have met with tlie same kind of aggregation in the sarcode of the superficial chambers of
OrhHolites (Plate IV, fig. 1), the spherules averaging about l-3200thof an inch in diameter.
Lying in the midst of the sarcode of the same animal, 1 have occasionally found other bodies
(fig. 2, /< — (/), sometimes resembling simple cells, sometimes like cells undergoing binary sub-
division, having a firm envelope, and retaining the crimson hue of the animal substance even in
spirit-specimens ; their diameters varied between 1 -650th and l-300th of ai^ inch. These seem
analogous to the dark splierules observed by Scliultze (xcvii, p. 27) in certain Rotnlla, some-
times occupying all the chambers (fig. 3), in other instances confined to the last one or two; the
ordinary sarcode co-existing in the same shells, but not putting forth pseudopodia. These
spherules were composed of a collection of dark molecular matter, not enclosed in a distinct
membrane, but held together by some uniting medium ; and they were especially remarkable
for their resistance to reagents, not being acted on by sulphuric, nitric, or hydrochloric acids, or
by boiling alkalies. The Botalice containing these dark spherules were isolated by Schulze, and
kept for many weeks, but no change could be observed in them ; and it must at present be
regarded as quite uncertain whether the foregoing phenomena have any relation to the
reproductive process.

49. More satisfactory information was subsequently obtained by the same excellent observer
(xcvni) in regard to the production of the young of j\fUUil(i. Having obtained some
large living specimens of the ii-UocuUni' form of Miliola, he kept them for some time under
inspection, and found that some of them, after remaining adherent to the sides of the glass
vessel during from eight to fourteen days, became invested with a brownish, slimy matter,
which more or less completely obscured the view of the external characters of their shells.
After the lapse of some days longer, minute, sharply-defined granules could be seen in this
substance with the aid of a lens (Plate IV, fig. 4, a), and these gradually loosened themselves
from the soft enveloping mass, and separated further and further from the shell wliicli it
surrounded. Microscopic examination of these corpuscles, of which as many as forty were
counted round a single progenitor, proved that they were young MUiolce. When viewed by
transmitted light, thev presented a pale, yellowish-brown, calcareous shell, consisting of the

38 OF THE RHIZOPODA IN GENERAL.

central globular primordial chamber in which all Foraminifera seem normally to commence,
partly surrounded by a closely applied tubular part, not separated from the preceding by any
distinct septum (fig. 4, b). In a short time, the young animals put forth their pseudopodia
from the aperture of the shell, and crawled about upon the surface of the glass. The shell
was sufficiently transparent to enable the contained sarcode-body to be examined with high
magnifying powers ; and it was seen to consist throughout of the ordinary protoplasmic
substance, without any vestige either of nucleus or of contractile vesicle. The latter half of
the tubular volution of the young shells was observed not to be completely occupied by the
animal substance, whilst the central portion was densely filled, the oil-particles especially
accumulating in the latter position. When the calcareous shell of the parent Miliola was
carefully broken up, it was found to contain only trifling remains of fine granular sarcodc,
Avhich did not put forth anv pseudopodia, and in which no vestige could be traced of anything
resembling a young animal in progress of development. Hence it would appear as if the
principal part of the body of the parent had been transformed into the bodies of the brood of
young, which seem to quit the parent in an advanced condition, probiibly acquiring their
shelly envelope before leaving that of their progenitor. — Prof. Schultze has since (xcix, p. 320)
had the opportunity of observing a like phenomenon in the case of a small RoUdia, about
1-1 00th of an inch in diameter, which was living attached to the interior of a glass bottle.
The yellowish-brown contents, especially of the larger chambers, exhibited a peculiar coarsely
granular consistence, observable even with a strong lens ; and on breaking up the shell, which
contained ten chambers, twenty or thirty small Polythalamia were found in its interior. These
were all of equal or nearly equal size, and consisted of three mutually adherent, nearly
globular chambers, of which the first and innermost was the largest, and was filled with large
pigment-vesicles, resembling fat-globules, while the other two were colourless. The shell
was very thin and brittle, and corresponded in the dimensions of its chambers with the
first-formed portion of that of the parent. On watching other individuals which presented
the same coarsely granular appearance, it was observed that a multitude of granules suddenly
appeared in their neighbourhood, which proved, on examination, to be young Polythalamia,
of the same size and form as those artificially freed from their parent, and only differing from
them in showing the yellow colour in the second as well as in the first chamber. Whether
they made their escape by the rupture of the shell of the parent. Prof. Schultze did not
succeed in determining with certainty, but appearances favoured the belief that such was their
mode of exit. — Dr. T. Strethill Wright has lately (cxii, p. 362) confirmed an observation
formerly made by Ehrenberg, as to the presence of the young of SpirilHna vivipara in the
interior of the shell of the parent.^I may add that I have in my possession a
number of very young specimens of Orbitolitcs, consisting simply of the primordial chamber
and the one immediately surrounding it (Plate IV, fig. 22), which were removed by Mr. W.
K. Parker from the deeply-channeled margin of one of these large plicated forms of Orh'i-
fnlites that present themselves in certain localities of the Polynesian Archipelago. In that
specimen they occurred in considerable numbers.

50. Whether the transformation of the sarcode-body of the parent into the substance of the
young occurs in the foregoing cases as the result of anything like a sexual act, or is e9"ected
(like the formation of zoospores among Protophytes) simply by the breaking up of the original

REPRODUCTION OF RHIZOPODA. 39

protoplasmic mass, is a question as to which there is not at present the sHghtest evidence on
either side ; and it is much to be desired that observers who have facihties for the study of
the reproduction of the Formmni/era should systematically and perseveringly investigate it.
The only observations yet recorded, that indicate the existence of a sexual process in Forami-
nifera, are those of Dr. T. Strethill Wright (cxii), who states that on examining a great
number of specimens of Gromio, ('ornuspira, Miliola, BoMia, and Orhuliiiu, he has repeatedly
discovered bodies which correspond to the " primitive ovum " of ^c«/(^//(«. They consist of
transparent spheres or ovoids, formed of a finely molecular substance, in which, however, the
molecules are masked or rendered indistinct by the highly refractive matter in which they
are imbedded. He was never able to detect either germinal vesicle or germinal spot in the
living specimens ; but in a specimen of Trunratuhva which had been hardened in spirit,
decalcified by dilute nitric acid, and then mounted with strong heat in Canada balsam (PI. IV,
fig. 5), four of the segments (r, c, c, c) each contain an ovum, which shows a germinal
vesicle and spot with the utmost distinctness, whilst the rest («/, d) present the usual
appearance of granular, low-refracting sarcodc. The ova of Gromia are small enough to
escape by the aperture of the "test;"' and as young Groiuia: are met with slightly larger than
these ova, it seems probable that the ovum is at once transformed into the body of the ofi^spring,
and that it directly acquires an envelope. But in Orhulina and Trtmcattdina the ova are of
much larger proportionate size, having in the latter case as much as ten times the diameter of
the primitive segment, and being far too large to escape by the aperture of the chambers
which contain them. Hence it is considered probable by Dr. Wright that the ova of these
genera undergo a polymorphic development of many months' duration, similar to that supposed
by Carter to occur in Amwha verrucosa (^ 47) ; and that each ovum becomes transformed by
fission (of which process he detected indications) into numerous amoeboid zooids, which escape
through the openings of the shell and form the primordial segments of future Rhizopods. The
observations of Prof. Schultze upon Rolalia, however, would rather lead to the inference
that the segments into winch the ovum breaks up remain in connexion with each other, and
constitute, not the primordial segment only, but the segments immediately succeeding it, in
each of the young, and that these escape by the rupture of the shell of the parent. — Specimens
occasionally present themselves which indicate that a partial binary fission of the germ may
take place at a period anterior to the calcification of the wall of the primordial segment.
Thus Prof. Williamson (ex) has described a twin monstrosity of Entosolenia (fig. 32, a), and
a similar example of Z)«^/«//«« (fig. 49), which have obviously originated in an incomplete
subdivision of the primordial segment ; and he states (p. xi) that " whenever such specimens
occur, it invariably happens that the two halves of the twin organism belong to the same
variety or type," — a fact of some importance as indicating that the transmission of varieties
is eS"ected, as in Plants, by those processes of subdivision which take place under the form of
fission or gemmation, whilst the origination of varieties is rather to be looked for in sexual
generation. Some curious examples of the same kind of " monstrosity by excess," occurring
in Orbitolitefi, have been described and figured by myself (xiii) ; and in those cases also.
Prof. WiUiamson's general statement was fully borne out.

CHAPTER III.

OF THE FORAMINIFERA GENERALLY ; THEIR CHIEF TYPES OP STRUCTURE AND
MODES OF GROWTH, AND THE PRINCIPLES TO BE FOLLOWED IN THEIR
CLASSIFICATION.

5L The group of Rhizopods which is known under tlie designation Foraminifera has
been shown in the preceding Chapter to be distinguished from the other great divisions of its
class, not only by that investment of the sarcode-body with a calcareous shell which constitutes
its most easily I'ecognised feature, but by such a peculiarity in the condition of the sarcode-
body itself, as seems to justify a marked separation of the animals which exhibit it from those
formed upon the type either of the Amwha or the Actinophrijs. That peculiarity (it may be
well to repeat) essentially consists in the absence of differentiation in the semi-fluid proto-
plasmic substance of which the body is composed ; its homogeneousness being especially
manifested in the freedom and minuteness with which its pseudopodial extensions subdivide,
and in the readiness and completeness of their coalescence wherever they come into contact
with each other, so as by their ramification and mutual inosculation to form a living-
network, along the threads of which a circulation of granular particles is continually taking
place. Of the Order Reticularia thus constituted so few other forms exist, that
it may be almost said to be synonymous with the group of Foraminifera; and it may
indeed be questioned whether in a classification based on physiological principles there is any
adequate ground for separating from the calcareous-shelled Miliola (^ 35) either Gromia
(•[ 33) whose" test" is membranous (probably chitinous), or Licbcrkuhnia (% 32) which has
no firm covering at all. So far as we yet know, there is no difference whatever between the
animals of these three types ; and to class them separately, still more to arrange Gromia and
Layyim (as Schultze has done, xcvii, p. o2) \i\\}a Arcella z.'ixADiJjhigia, on account of the unilo-
cular condition of the " test," would seem just as unnatural as it is now admitted to have been
to separate Hydra from the compound Hydroida, and Actinia from the compound Helian-
THOiDA, and to group together Hydra and Actinia as naked solitary polypes, whilst their
composite representatives were classified according as they form horny or calcareous
skeletons. Until, therefore, some more adequate ground bf differentiation shall have
been established than any at present known, the group of Foraminifera may be
considered as really coextensive with the Order Rhizopoda reticularia; and there

PRINCIPLES OF CLASSIFICATION. 41

seems the more reason for including Gromida and even Lieherkiihnia within its limits,
when it is borne in mind that in the limitation of the origin of the pseudopodia to one
part of the body these forms bear a closer relationship to the Foraminifcra of the MUioUne
series, than the latter do to those of the liotalinc, in which the pseudopodia seem to extend
themselves equally from any part of the sarcode-body.

52. Before enlarging upon the value of the differential characters just alluded to —
which will be shown to have such an important relation to certain peculiarities in the struc-
ture of the Shell, as to justify the employment of these as characteristics of the fundamental
divisions of the group — we must stop to inquire how far the separation of the Monothalaiiious
or Unilocular Foraminifcra, as an order distinct from the PoI^fJialamous or Multilocular (a
separation which has been adopted by D'Orbigny, Schultze, and Bronn), is to be regarded as
based on a right appreciation of their mutual affinities. It has been seen that, in common with
all the lower forms of animal and vegetable life, the Rhizopoda tend to multiply by a separa-
tion of continuously growing parts of their bodies, which may take the form either oi fssioii
or of gemmation, according as the original bod)'^ undergoes subdivision, or as it puts forth an
extension which eventually detaches itself. Among the Foraminifcra proper, whose bodies
are enclosed in unyielding shells, multiplication by fission cannot take place, except in that
early stage of existence in which the shell is not as yet consolidated (5[ 50) ; but extension
by gemmation may go on without limit. The progressive growth of the sarcode-substance
causes a portion of it to project beyond the aperture of the shell ; and this projecting portion
possesses all the attributes of the body of which it is an extension, and can maintain its exist-
ence with equal readiness either in a separate state (1[ 39) or in continuity with the stock of
which it is an offset. Although, therefore, there are certain types of Foraminifcra in which
such offsets appear invariably to separate themselves before the consolidation of their shell, so
that the original body never adds to the number of its segments and the shell remains
" monothalamous," — whilst there are others in which they ordinarily remain in connexion with
the original stock, so as progressively to augment the number of its segments and of the
chambers of its " polythalamous shell," often to an indefinite extent, — there is no such essential
difference between the physiological conditions of the newly formed segment in the two cases,
as would be required to justify the erection of the Monothalamia into a distinct order.* More-
over, we find that between these two groups there are gradational affinities of such a kind as
to render it impossible to separate them by a decided line of demarcation. For, on the one
hand, there are certain Monothalamous Foraminifcra which may be regarded as potentially
Polythalamous, the body and shell having the power of indefinite extension, but not exhibiting
any distinct segmentation; as is the case with Cornuspira and Spinllina, of which the former
is intimately related to the least speciaHsed forms of Miliola {% 104), whilst the latter is
scarcely less closely related to certain Rotalia. On the other hand, since there are certain
Polythalamia (f 40), the successive chambers of whose shells are so slightly connected

* No botanist would think of separating from their natural allies, and ranking together as a dis-
tinct order, those Plants which habitually propagate themselves by detached gemnue, such as Lunularia
vulgaris and Lemiia gibba (which are only known to reproduce themselves after this fashion), or
Dentaria bidbifera, Gtobba amarantina, and Lilimn bulbifenim.

6

42 OF THE FOEAMINIFERA GENERALLY :

as to be easily separable from each other by accidental violence, and of which the animals
can maintain their lives jnst as well when they are thus broken up into distinct segments
as when retaining their original connexion, such may be regarded as poientially Mono-
thalamous ; and the fact that the segments of sarcode, as they were successively budded forth
from the stock, formed their shelly investments before instead of after their detachment from
it, can scarcely be admitted by the physiologist as alone justifying an ordinal differentiation
which is not borne out by other structural or physiological diversities.

53. It was not unnatural that, in seeking for a basis on which to found an arrangement
of the multitudinous forms of Foraminifera which he for the first time brought together under
one distinct category, M. D'Orbigny should have attached primary importance to characters
so easily recognised as those which are produced by diversities in the plan on which the suc-
cessive segments are added one to another. For the varieties of form thus produced seem at
first sight easily capable of being reduced to a small number of primary types ; and it is only
by such a laborious and conscientious comparison of osculant forms as formed no part of M.
D'Orbigny 's method of study, that the essential conformity in plan of growth is discovered
which often exists between organisms arranged by him under different orders ; whilst it is
only by an equally painstaking examination of the internal structure of the shell, such as seems
never to have been even thought of by M. D'Orbigny, that those very marked characters are
brought to light, which often separate by the widest interval organisms grouped by him under
the same order, and which bring these respectively into intimate relationship with others
whose place in his series is very remote. Thus, when we come to speak of the genus
CristcJlaria, we shall find that it comprehends a series of straight, curved, and spiral forms,
agreeing with each other in all essential particulars save the direction of their axis of growth,
and presenting such a continuity in the gradation from the straight to the curved, and from
the curved to the spiral, as prevents any decided line of demarcation from being anywhere
drawn among them. So, again, we shall find that although, on the ground of conformity in
their plan of growth, Orbitolites and Cydochjpeus would be grouped together by M. D'Orbigny
in his order Ci/closter/ues, whilst Oriiculiiia, Penerojilis, and Operculina are placed in his order
Helicostef/ues, and Heferostegina in his order Enfomostef/ues, a careful comparison of the
essential features of their structure shows that not only have Orbitolites and Ci/clocli/peas
nothing in common but their cyclical mode of growth, but that Orbitolites is most intimately
related to Orbiculina (which often takes-on the cyclical mode of growth), and through it to
Peneroplis, whilst CyclocJypeus is scarcely less intimately related to Heterosteyina and through
it to Operculina. It may, in fact, be most safely asserted, thatj'Vaw of groicth is no more to be
regarded as an exponent of the really natural afiinities of the several generic types of
Foraminifera, than the number of stamens and pistils is of the natural affinities of Phanero-
gamous plants. The system founded upon each of these bases will doubtless, in many
instances, bring together types which have a real affinity to each other, simply because the
characters in question sometimes coincide with those of more essential value ; but such coin-
cidence is (so to speak) accidental ; and it much more frequently happens in the one as in
the other of these artificial systems, that they separate by a wide interval types which in
reality are closely related, whilst those which they bring into nearest proximity are essentially
diverse in organization.

PRINCIPLES OF CLASSIFICATION. 43

54. The foregoing remarks are scarcely less applicable to the classifications of Professors
Schultze (xcvii) and Bronn (xi) than they are to that of M. D'Orbigny; since by them,
as by him, the jjiau of f/roxolh is regarded as the fundamental basis of S3'stematic arrangement,
so that their primary divisions are eminently artificial. They have been guided, however, in
their subdivision of Orders into Families by a higher appreciation of the characters furnished
by variations in the texture of fl/e hJicII, than was entertained by M. D'Orbigny ; and they have
thus been led to a more natural grouping of generic forms than his classification usually
presents. — As neither of their systems, however, has yet found its way to general acceptance, it
scarcely appears necessary here to enlarge upon their defects ; these being necessary results
of the imperfect method of study whicli tlieir authors have followed; and the object of the
present work being to sTibstitute a classification, whicli, however incomplete, shall, at any rate,
present an approximation to a natural system, as being based on the whole aggregate of the
ascertainable characters of the several types, instead of on a single feature which affords no
reliable indication of their real aflSnities.

55. It is now universally admitted by Philosophical Zoologists, that the importance of the
characters furnished by the f^Icrleton, whether internal or external, of any animal, depends
entirely upon the relations which they bear to its general organization ; and that hence the
adoption of any such characters as a basis for classification can only be justified, when their
accordances and differences can be shown to be indicative of corresponding accordances and
differences in those parts of the organism whicli are of higher physiological import. Thus
the possession of a hivahe shell is universally admitted as differentiating the Mollusks which
bear it from those whose shell is univalve, the whole plan of structure of the animals in the two
cases being obviously different. But among " bivalve'' Mollusks there are two very distinct
types of structure (the Lamellibranchiate and the Palliobranchiate), whose essential dissimi-
larity, being only revealed by anatomical inquiry, would never have been recognised by the
mere Conchologist ; although, when he has once made himself acquainted with these types, he
finds no difficulty in distinguishing the shells they respectively include by the special
characters which they severally present. So among " univalve" Mollusks there is not less
diversity of type, shells composed of a single piece being found among Gastcropods, Ptero-
pods, and Cephalopods ; and the conformation of the shell is here so much less intimately
related to that of the animal by which it is constructed, that it is not always possible to refer
a shell with certainty to its proper place while the nature of its animal inhabitant is unknown.
Further, " univalve" shells are formed also by Annelida, and there are no well-defined characters
by which the tubes of a Serjjula (Annelid) and these of a Vermetm (Gasteropod Mollusk) can be
distinguished one from the other ; so that in a system of classification founded ujion the shell
alone they would be placed side by side, as would also the Crustacean Cirrhipedes and the
Gasteropod Chitons, because both these tribes of animals have their bodies protected by
multivalve shells. Among Zoophytes, again, whilst the " lamelliform" structure of the stony
Corals is so uniformly related to the Aetiniform type of organization, that the existence of
that structure in the oldest fossil affords a sure key to the nature of the animal which formed
it, the polyparies which constitute the skeletons of animals of the Ahyonian type are so
diverse in their composition and arrangement, that it only becomes safe to predicate the

44 OF THE FORAMINIFERA GENERALLY :

animal from the polypary, when each type of skeleton has been examined in connection with
the soft body it supports. On the other hand, we not unfrequently find that a close resem-
blance in the structure of the polypary masks an essential diversity in the organization of the
animal ; certain horny skeletons of H^/drosoa being scarcely distinguishable from those of
Poli/zoa, although the former belong to true Zoophytes, whilst the latter are members of the
Molluscous sub-kingdom.

56. It seems obvious, then, that no classification of Foraminifera can be thoroughly
satisfactory, which is based rather on the characters of their shells than on those of the
animals by wliich those shells are formed ; and it is unfortunate tliat our knowledge of the
latter is as yet so imperfect, as to afford us but a ver}^ slight foundation for a natural arrange-
ment of the group. It may be questioned, indeed, whether the extreme indijferenHsm of
structure which seems to be a general characteristic of the Rhizopod type and to reach its
acme in the Foraminifera, will not always prevent the systematist from finding the study of
the animal of much avail to him ; and whether he will ever be relieved from the necessity of
placing his chief reliance on those features in the structure of the shell, which may be
regarded as most surely indicating the potentialities of the apparently homogeneous jelly-like
mass which it encloses. Such, at any rate, must be his method of procedure under existing
circumstances ; and as there is at present nothing to be added to the general account alread}'
given of the structure and life-history of the sarcode-bodies of the Foraminifera, our attention
will be now directed to the characters furnished by the investments which they form, with a
view to determine what are those on which the primary and secondary subdivisions of the
group may be most satisfactorily based.

57. Texture of the Skell. — In the shells of Foraminifera, as was correctly pointed out by
Prof. Williamson (ex, p. xi), three very distinct varieties of texture are easily recognisable :
the porcellanous, Xhe hyaline or vitreous, and the arenaceous. — In the first of these varieties the
shell, when viewed by reflected light, presents an opaque-white aspect, which bears a strong
resemblance to that of porcelain, especially when (as in Penerojjiis) its surface is highly
polished. When thin natural or artificial laminae of it, however, are viewed with transmitted
light, the opacity gives place to a rich brown or amber -colour, which seems to be imparted
by the animal matter that is united with the calcifying deposit, the colour of the sarcode-body
being usually the same as that of the shell. In a few instances both the shell and the animal
body have a rich crimson hue. No structure of any kind can be detected in this kind of
shell-substance, which is apparently homogeneous throughout. When shells of this character
are decalcified by dilute acid, a delicate, gelatinous-looking substratum of animal matter is
left, very distinct in its aspect from the sarcode-body which the shell included (Plate IV, fig. 14).
This, in fact, seems to bear the same relation to the protoplasmic substance, that the cellulose
wall of the vegetable cell bears to the " endoplast" from the surface of which it is excreted ;
and just as in Biatomacece the consolidation of that exudation by silex forms the beautiful lorica
characteristic of that group, so here does the consolidation of an analogous excretion-layer by

alcareous deposit form the shellv wall of each segment of the animal. Although the shells
of the porcellanous type often present the aooearance of bemg perforated with foramina, yet
this appearance is illusory, being due to a mere " pitting" of the external surface, which pitting

PRINCIPLES OF CLASSIFICATION. 45

though often very deep, never extends through the whole thickness of the shell. Some kind
of inequality of that surface, indeed, is extremely common in the shells of the porcellanous
Foraminifera. Very frequently it presents an alternation of ridges and furrows, such as dis-
tinguishes certain varieties o^MilioJa (Plate VI, figs. 3, 4) ; and this alternation is so regular and
constant in Prawo/V/s (Plate VII, fig. 18), and in the first-formed segments of Vertebralina
(Plate V, figs. 17 — 25), as to be peculiarly characteristic of those types. In other instances,
especially among the Miliohc, we find the surface marked by depressions which may vary
greatly in size and in arrangement (Plate VI, figs. 13, 14), being sometimes minute puncta-
tions, in other cases being lai'ge areolae ; being sometimes scattered with no apparent regularity,
in other instances disposed with the most exact symmetry. But no difference of texture
accompanies any of these inequalities of the surface, the raised and depressed portions being
alike homogeneous.

58. In the shells of the vitreous or hyaline type, on the other hand, the proper shell-
substance has an almost glassy transparency ; which is shown by it alike in the thin natural
laminas of young specimens, and in artificially-prepared sections of such as are thicker and
older. It is usually colourless, even when (as is often the case with Rotalia) the substance
of the animal is deeply coloured. In certain aberrant forms of the Rotaline type,
however, we shall see that the shell is commonly, like the animal body, of a rich crimson hue.
But notwithstanding the transparence of their substance, these shells derive an adventitious
opacity from being channeled out more or less minutely by tubular perforations, which, when
occupied either by air or by any substance having a refractive power different from that of
the surrounding shell, interfere with its power of transmitting light, and cause it to reflect a
large part of that which falls upon it. Their effect varies, however, according to their degree
of minuteness and the closeness of their arrangement. Thus, in Rotalia, in which they are
commonly almost 1 -3000th of an inch in diameter and somewhat more than that apart
from one another (Plate XIII, fig. 1, a), the hyaline transparence of the thin shell makes
itself apparent between them, and imparts to its entire surface a vitreous aspect.
In Opercidina and Cycloclypem, on the other hand, in which the average diameter of
the tubuli does not exceed l-10,000th of an inch, and their distance from each other is
not much greater, every part of the shell that is traversed by them presents a semi-
opacity, which only disappears when extremely thin sections are made in a direction
exactly transverse to the axis of the tubes, so as to enable the transparence of the intervening
substance to display itself without interruption (Plate XIX, fig. 4). It often happens, how-
ever, that certain parts of the shell are left unchanneled by these tubuli ; and such are at once
distinguished, even under a low magnifying power, by the readiness with which they allow
transmitted light to pass through them (Plate XVII, figs. 12, 13, aa, da, U\ and by the peculiar
vitreous lustre they exhibit when light is made to fall obliquely upon their surface. In shells
formed upon this type we frequently find that the surface presents either bands or spots which
are thus distinguished ; the non-tubular bands usually marking the positions of the septa (Plate
XVII, fig. 1), and being sometimes raised into ridges, though in other instances they are either
level or somewhat depressed, whilst the non-tubular spots may occur on any part of the
surface, and are most commonly raised into tubercles (Plate XV, fig. 5, and Plate XIX, fig. 5),
which sometimes attain a size and number sufficient to give a very distinctive character to the

46 OF THE FORAMINIFERA GENERALLY:

shells that bear them. In shells of this type, however, which have been long dead and exposed
to the action of sea- water, the vitreous transparence often gives place to a lustrous white
opacity, that is particularly striking in the prominent tubercles ; as is remarkably shown in the
tuberculated variety of Plamrhdina vulgaris (Plate XIII, fig. 1 5) . The texture of the shells of
this type is much firmer tl;an that of the porcellanous shells ; approaching closely to that of the
inferior forms of dentine, or to that of the terminal portion of the crab's claw.

59. Between the comparatively large apertures which are common in the Rotaline type,
and the minute tubuli of the OpcrcnVine, there is such a continuous gradation as indicates that
their mode of formation, and probably their uses, are essentially the same. In the former it
has been demonstrated by actual observation that they allow the passage of pseudopodial
extensions of the sarcode-body through every part of the external wall of the chambers
occupied by it ; and there is nothing to oppose the idea that they answer the same purpose
in the latter, since, minute as they are, their diameter is not too small to enable them to be
traversed by the finest of the threads into which the branching pseudopodia of Foraminifera
are known to subdivide themselves. And it seems the more likely that they answer this
purpose, when attention is given to the remarkable continuity which they exhibit through a
considerable thickness of shell, formed of numerous lamellffi that seem to have been added at
successive periods of growth (Plate XIX, fig. 3). Now, if this be the case, it is not difficult to
account for the production of a texture closely resembling that of dentine, without having
recourse to the hypothesis (xxv, p. 421) of a higher organization in the bodies of
these animals than that which we have other grounds for admitting. For if the
shell-substance be, as there seems reason to believe, an excretion from the |3rotoplasmic
mass of which the body itself is composed, each new lamella, as it is added to the pre-
ceding, will mould itself upon the pseudopodia that issue from the orifices of the subjacent
surface ; either some difference in their composition, or the activity of the changes con-
tinually taking place in their substance (^ 34), preventing them from being involved
in the consolidation which takes place ai'ound them. We have an illustration of the same
kind on a larger scale, in the extension of the straight branches of the canal-system which
pass through the solid masses of shell-substance that occupy the umbilical regions in the shells
of Calcdrina and Fohjdomella (Plate XIV, fig. 3, and Plate XYI, fig. 3) ; the successive accretions
of vitreous material being so disposed around the extensions of the sarcode-body which occupy
these passages, as to preserve their continuity throughout, and thus to maintain the most
direct relation between the parts of the canal-system most deeply buried beneath these accre-
tions, and the external surface from which they become further and further removed. If this
should prove to be the true account of the formation of the dentine-like tissue produced by
the higher type of Foraminifera, it will deserve consideration whether a like explanation may
not be applicable to the formation of analogous calcified tubular tissues in animals much more
elevated in the scale ; especially since there is increasing reason to believe that the develop-
ment of such tissues takes place after a far simpler fashion than has been commonly
supposed, and that their foundation is laid in a homogeneous blastema, rather than in a
matrix possessing distinct organization.

60. Besides these two principal types of shell-structure, another is met with in certain
groups of Foraminifera, which is designated as the arenaceous; the shells being formed, either

PRINCIPLES OF CLASSIFICATION. 47

partially or wholly, not of a calcareous exudation from the sarcode-body, but of particles of
sand obtained from without, the cement with which they are attached together being all that
is furnished by the animal. The aspect of such " arenaceous " shells necessarily varies con-
siderably with the kind of material of which they are composed ; and the same t3'pe, inhabiting
several different localities, may thus present as many diverse fades. Thus, the TextularicB
dredged off the Canary Islands have their shells entirely composed of fine particles of a
black sand, apparently formed by the disintegration of volcanic rocks ; whilst those of the
Red Sea have shells of a grayish-yellow colour, the arenaceous particles of which vary much
more in their nature and origin. In some instances the particles are very uniform in size,
and are very methodically disposed (like those of which the tube of Pectinaria is made up) ;
so that the surface of the shell has almost the appearance, when sufficiently magnified, of a
tesselated pavement (Plate VI, fig. 41). This regularity — alike in size, form, and arrangement,
— is sometimes so remarkable as to have given rise to the supposition that the siliceous par-
ticles are not derived from external sources, but are formed by exudation from the surface of
the contained body. As, however, there is no siliceous " test " at present known to be formed
by an animal of this group, which is not obviously made up of an aggregation of distinct parti-
cles, instead of possessing the structural homogeneousness proper to the shells which are
undoubtedly formed by calcareous or siliceous consolidation, it would probably be correct to
say that the true " shell " of Foraiidnifera is imiformly calcareous, and that when this is
replaced by a siliceous " test " the materials of such test have been drawn together from
external sources. There are certain cases, on the other hand, in which the sandy paiticles
are less uniform in size and less regular in disposition, and are imbedded in a calcareous
cement which forms the essential constituent of the shell ; in these the arenaceous texture,
being superficial only, and to a certain extent accidental, has not that importance as a differ-
ential character which it bears when extending throughout the thickness of the shell.*

* The surface of certain Foramiuiferous shells (especially Globigerince) is not unfrequentlj'
studded with the minute rounded or oval bodies to which the name " coccolitlis " was first given by
Professor Huxley. (See his Appendix to the ' Report on Deep-Sea Soundings in the North Atlantic
Ocean, between Ireland and Newfoundland, made in H.M. " Cyclops," Lieut. -Com. Dayman, in June
and July, 1857.") These bodies have been since observed by Dr. Wallich (civ b), not only in the free
state, but adherent to the siu-face of minute spherical cells which seem to constitute a rudimentary
type of Foraminifera ; the uniformity of this adhesion being such as to lead almost necessarily
to the conclusion that it is a normal condition. These " coccoliths " are described by Dr. Wallich
as of an oblong form, concave on their internal aspect, and convex externally (Fig. I, s, i), their
average length being about l-3700th of an inch ; in some specimens there is but a single aperture in the
centre ; in others the aperture is double, the two portions being separated by a
delicate transverse band; and the external marginal surface, which constitutes a ■''"'• ^•

quoit-like oblong ring round the central perforated portion, is marked with radi- '•^^*;

ating striae. The spheres, to the surface of which the coccoliths are found adherent %^ \
at nearly regular intervals, are stated by Dr. Wallich to have a diameter from l-1.250th ale

to l-1600th of an inch, and to be composed of a sarcode-like substance enclosed W ^ y V5>s^
in a dehcate limitary wall, apparently consolidated by calcareous deposit (Fig. I, 1, 2, Cocoosplieres ;
1, 2). These bodies, to which he has given the name of " coccospheres," are 3, Jr, CoccoUtlis.

48 OF THE FORAMINIFERA GENERALLY:

61. To separate all the Foraminifera that form "arenaceous" shells from tliose of the
" porcellanous " and " hyaline " t3'pes, to which many of them obviously bear the closest
affinity, would be a violation of the first principles of a natural arrangement ; and yet we
shall find that there are certain generic types in which the sandy texture is a character of
great systematic importance. Thus, on the one hand, in the low " porcellanous " type Nuhc-
cularia, and in the "triloculine" and " quinqueloculine" forms of the more elevated type Miliola,
individuals frequently present themselves whose surface is rendered arenaceous by the im-
bedding of sandy particles in their ordinary calcareous shell-substance ; but for being thug
" rough-cast," such individuals would present the ordinar}' aspect of their i-espective types, to
which they are entirely conformable in every other character ; and it would be manifestly
improper to rank them apart on account of this trifling variation. So even when we find
truly arenaceous shells presenting the characteristic forms of the " hyaline " genera BuUmina
and Textularia, since we find at the same time that not only do they correspond in general
structure to the calcareous shells respectively peculiar to those genera, but are perforated like
them by regular pores for the passage of pseudopodia, we feel that we have no right to dis-
sociate what are manifestly nothing else than varieties of a common type. But when, on
the other hand, we find that certain assemblages of forms, constituting well-marked generic
types, can be uniformly characterised by the possession of "arenaceous" shells, — as is the
case with Trochammina, ValviiUna, and Liiuola, — it becomes obvious that this peculiarity is to
be regarded as a distinctive feature of higher value, since it marks a fixed and decided phy-
siological condition, the occurrence of which elsewhere is only occasional or incomplete. The
absence of any pseudopodial pores in the walls of the chambers of the shells of this group shows
their affinity to be rather with the porcellanous than with the hyaline series, notwithstanding
the very close resemblance in form which some of them present to particular types of the
latter, — Valvulina, for example, to BuUmina, certain Lifuola to Nonionina, and TrocJiammina
to SpirU/ina.

62. Turning now from the ultimate texture of the shell to its conformation, we have to
inquire whether there are any fundamental and essential diversities in its mode of increase,
which can be advantageously used as difl'erential characters. It may be stated as an un-
questionable fact, that the shelly casing, once formed to any portion of the sarcode-body, cannot
be enlarged by interstitial growth ; and hence it can only be adapted to the augmenting
dimensions of that body, by addition to the part already formed. In the greater part of the

Fig. II.

sometimes united in series, after the manner of certain forms of

Foraminifera ; thus in Fig. II, i, is shown a Nodosarian series of four

equal cells ; whilst at ;; is seen a Textularian series of seven cells,

which increase regularly in diameter from l-1350th to l-450th of an inch.

The " coccoliths " do not appear to be attached to the wall of the " cocco-

sphere" in any other way than by gelatinous adhesion ; and hence they

are very easily detached, so as to form a considerable proportion of

Coccosphcies, with attached m^ny deep-sea deposits. Similar bodies have been found in Chalk by Mr.

coccoliths, growins; (1) on

the Nodosarian, (2) on the ^" ^°''^y-

Textularian type.

PRINCIPLES OF CLASSIFICATION.

49

" nioiiollialamoiis " I'oramiuifera, the contraction of the aijerture entirely forbids the enlarge-
ment of the ca\ity by any sucli addition, but those spiral forms in which there is no such
contraction are capable, like t!ie tubular shells of Annelids and certain Mollusks, of bcin"-
indclinitely extended ; and it is simply because of its absence, that they present no indication
of the segmental division which would otherwise be marked by a transverse septum every time
that a longitudinal addition is made. This is the case with the genera Cormcsjjmi, Trochammina,
and SpirilUiiri, which arc respectively the porcellanous, arenaceous, and hyaline representa-
tives of the simply spiral plan of conformation ; and it is obvious that, although structurally
" monothalamous,'' these genera are in reality more nearly allied in their capability of
unlimited growth to the " polythalamous" series. The " polythalamous" shells are formed, as
already explained, by the repeated gemmation of the sarcode-body ; and it usually (though
by no means constantly) happens that the successive gennnaj increase in size, so that each
chamber is larger than the one which preceded it. The simplest types of Pohjthalntnki arc
those in which the segments of the shell have only an external adhesion, the cavities of their
chambers having no communication with each other ; as is the case in the im^jcrforatc series
with Daciz/Jopora and Aclcidaria, and in \\\q perforated with Glob'igerina. Save in these types,
however, the cavity of each segment always communicates with that of the segment from
which it is budded off ; and this it may do merely by the apertural neck of the older segment,
which dilates into the globular cavity of the newer, so that the succession of segments is
united into the semblance of a string of beads, as we see in some forms of Nodo>iaria (Plate
XII, fig. 2). More generally, however, the apertural portion of one segment is completely
embraced by the walls of the next chamber, in the manner diagrammatically represented in
Fig. Ill, where the primordial chamber is seen at and its aperture at n ; this aperture is
received into the second chamber, 1, the lateral
wall of which joins the anterior wall of the preced-
ing at h ; in like manner, the aperture «^ of the
second chamber is received into the third chamber

2, the aperture of this, «°, into the next chamber

3, and so on, the aperture n"^ of the last chamber
opening externally. — A great alteration in external
shape may be produced, without any departure from
the rectilineal plan of growth, by the still more com-
plete reception of the anterior portion of the older
chamber into the posterior portion of the newer; as
is shown in Fig. IV, wliich diagrammatically repre-
sents the " frondicularian" form of Nodosarina. —
On the other hand, a complete alteration in external configuration may be pioduced by the
substitution of a curviliiirar for a reclilliiear axis of growth ; the most ordinary type of the
former being a spiral, which may be either flat, like that of a Nm/tilns, or may coil around a
longitudinal axis, like that of a Trocluis. Between the rectilineal and the spiral forms of axes
of growth a complete gradation is presented in the Nodosarine series. In Fig. VII we see
that the relations of the chambers may be essentially the same in the spiral as in the recti-
lineal type ; the septal plane that divides each chamber from its successor being formed
solely by the anterior wall of tlie older, which serves as the posterior wall of the newer.

Fig. III.

Fig. IV.

50

OF THE FORAMINIl'ERA GENERALLY,

This is the case tiiroughout the 'porcellanom series and with the lower forms of the vitreous
series. But in the highest types of the latter we find that each chamber of the spire has a

Fig. V

Fig. VI

Fig. VIII.

complete shelly envelope of its own, the new segment forming a posterior wall, which
applies itself to the anterior wall of the preceding segment, so that each septal plane
(except that of the last chamber) is composed of two lamella;, as is shown in Fig. VIII.
— The same difference exists among the Polt/tlialauiia formed upon the cijdkal plan of growth,
which is ordinarily the result of the gemmation of the primordial segment not on one side
only, but from every part of its circumference, and the subsequent repetition of the same
mode of increase (see Fig. XXIV, p. 108). For in the cyclical forms of the porcelhnio/'s series
the successive annuli are joined, each to its predecessor, in such a manner that the external
wall of the latter serves as the internal wall of the former, as is seen along the lines a a, a a,
Fip-. V; and the septa dividing the adjacent chamberlets of the same annuli are also single.
In the cyclical forms of the vifreo//s series, on the other hand, each chambcrlet has its own
proper wall, as is shown in Fig. VI : so that not merely the annular but the radial septa are
all double.

63. But this is by no means all ; for in the higher types of the hyaline or vitreous series
we frequently meet with an " intermediate" or " supplemental" skeleton, formed by a secondary
or exogenous deposit upon the outer walls of the chambers, by which they receive a great
accession of strength. This deposit not only fills up what w^ould otherwise be superficial
hollows at the junctions of the chambers, or (as in PolydomeUa) at the umbilical depression,
but often forms a layer of considerable thickness over the whole surface, thus separating
each whorl from that which encloses it (Fig. YIII, d) ; and it is .sometimes prolonged into
outo-rowths that give a very peculiar variety to the ordinary contour, as in some varieties
of Botalia and FohjstomeUa, but most characteristically in Calcanna (Plate XIV, figs. 1, 2, 8)
and the stellate form of Tinopori's (Plate XV, figs. 5—9). This intermediate or supplemental
skeleton, wherever developed to any considerable extent, is traversed by a set of "canals,"
which are usually arranged upon a systematic plan, and are sometimes distributed with
considerable minuteness. The passages which make up this " system" are not true vessels, but
are mere sinuses, left in some cases by the incomplete adhesion of the two contiguous walls
which separate the adjacent chambers, and in other cases apparently originating in the
incomplete calcification of the sarcode which forms the basis of the solid skeleton ; certain

PRINCIPLES OF CLASSIFICATION. 51

portions of that substance remaining in their original condition, so as to maintain a communica-
tion between the contents of the chambers and the parts of the calcareous skeleton most
removed from them, analogous to that which the Haversian canals afford in the case of latninte of
bone not in the immediate vicinity of a vascular surface. As, therefore, the development of the
Haversian system is related to the thickness of the bone-substance to be nourished, so does that
of the canal-system in Foraminifera seem to be related to the amount of the consolidating
substance which constitutes the supplemental skeleton. There is good reason to believe that
these canals are occupied in the living state by prolongations of the sarcode-body, which pass
from the chambers into the portions of the system in nearest relation to them, and proceed to
its peripheral extensions ; and they are largest and most numerous where nutriment has thus
to be conveyed to parts of the supplemental skeleton, which (like the outgrowths of Calcarina)
are very far removed from the segments of the ordinary sarcode-body. Now, although it is
only in the largest and most developed types of the hyaline series, that we meet cither with a
distinct " canal-system" or witli any considerable amount of that intermediate deposit which
it nourishes, yet the jDresence of these two peculiar features most strongly differentiates those
types from such of the porcellanous series as most nearly resemble tliem in general plan of
growth, and to which, according to any classification essentially founded on that character,
they would be most nearly approximated, — as, for example, the hyaline Ojjerculina from the
porcellanous Pciieroplls, the hyaline Cydodypeas from the porcellanous Orbitolites.

64. Another strongly marked difference, that seems no less obviously related to the
physiological condition of the animal than the perforation or non-perforation of the shell, is
observable in the degree of separation that exists between the segments of the sarcode-body
in the two series respectively ; this body even in the most complex types of the imperforate
shells being an aggregate of mutually related parts, whilst even in the simplest types of
the perforated these parts acquire a much higher degree of independence, so as to live much
more /';/• and by themselves alone. The key to this difference is furnished by the relative
size of the aperture, which indicates in the unilocular types the degree of readiness with
which the animal can extend itself into the medium it inhabits, whilst in the raultilocular it
indicates not only this, but also the relative amount of connection between the several segments
of the composite structure. Thus, when we compare the unilocular Gromia (which, though
possessing only a membranous " test," may be considered as physiologically representing the
unilocular type of the imperforate Foraminifera) with the unilocular Layena, we are at
once struck with the extreme narrowness of the aperture of the latter, as compared with
the wide, open mouth of the former (Plate II, fig. 2) ; and this difi'erence will be readily
understood, when it is borne in mind that in one case the principal aperture is supple-
mented (so to speak) by the' pores distributed through the whole of the globular casing that
encloses the body of the animal, every one of which allows the passage of a pseudopodium,
whilst in the other the sarcode-body, shut up within its " test," has no other means of com-
munication with the external world than that afforded by its single orifice. So, if we compare
the apertures of Niibecularia, Vertebralina, and Miliola with those of the Nodosarian series, we
find a no less striking contrast between the mere constrictions that mark out the segmentation
of the sarcode-body in the former, and the almost complete separation that exists between the
successive chambers in the latter. In Pmeroplis, again, although the apertural pores are

52 OF THE FORAMINIFERA GENERALLY:

individually small (Plate VII, fig. 18), yet their multiplication (which takes place proportionally
to the size of the chambers) renders the aggregate communication very free, as we see in the
deiidriftue variety, in which the pores are all gathered together, as it were, into one aperture
(Plate VII, fig. 1 ) ; and the contrast is very marked between the large si^e of this, and the extreme
narrowness of the fissure which forms the only constant communication between the chambers
of OpercuJina. The like contrast, in regard to the connection of the successive segments, exists
between Orbiculina, the spiral type of which may be described as a Pnirroplis whose principal
chambers are partially subdivided by transverse partitions, and Hcferosfet/ina, which bears the
like relation to Operciilina. And a no less striking difference exists, in this respect, between
Orbitolites, which is the most developed type of the imperforate series, and Ci/e/oc/ypei/s, which
holds a like position in the perforated ; the communications between the successive annuli in the
former, and between the outermost annulus and the exterior, being so numerous and free, as to
amount in the aggregate to a large apertural area, whilst in the latter they are so much more
restricted as to be not readily discoverable. This tendency to a more complete separation of
the segments sliows itself yet more strongly in regard to the transverse subdivision of the
principal chambers in Orbiculuia as compared witli Ili'tcroxti'gina, and in Orbitolite-s as com-
pared with Cydoclypeus ; for in the two imperforate types we find this transverse subdivision so
far from complete, that it resembles that of a long dormitory in which the beds (arranged in

rows on the two sides) are separated from each other by partitions
that extend from the walls towards the central line of the apart-
ment, but stop short of it, so as to leave a free passage from one
end of it to the other ; whilst in the two perforated types the
chamberlets of each row are entirely cut off from each other
laterally, communicating only with those of the rows behind and in front of them. Thus
we see that, whereas in the imperforate shells the nutrition of the entire body is
derived from the alimentary materials obtained l)y the last segment alone, every segment
in the perforated shells is capable of obtaining, at an}' rate, a portion of its supply for itself;
and hence a much greater degree of individualization of the segments is possible in the
latter case than in the former. We shall find tiiis contrast most strongly marked when
we come to compare the calcareous skeleton of OrbifoNfe-s- with that of Cydoclypeus ; the
former being, as it were, a concretionary framework, which grows up in the midst of and around
the sarcode-body for its support and protection, isolating its parts from each other no more than
is required for that purpose ; whilst in the latter each segment and sub-segment has its own
distinct and complete envelope, which seems (as it were) to be moulded upon its shape, any
interspaces being filled in by the intermediate skeleton, whose intervention between the two
layers of the double partitions renders the isolation of the chambers yet more complete.

65. Thus, then, we find that, alike in the intimate structure of the shell, in the presence
or absence of an " intermediate skeleton" and of a " canal-system" for its nutrition, in the com-
pleteness witli which each chamber is surrounded by its own proper wall, and in the degree
of its separation from adjacent chambers — all which features are as characteristic of every
individual portion of the shell as they are of the shell as a whole, and are evidently in intimate
relation with the physiological condition of the animal that inhabits it, — a very decided
differentiation may be established between the two series of imperforate and perforated

PRINCIPLES OF CLASSIFICATION. 53

FoRAMiNiFERA ; and this primary differentiation will be found so constantly to harmonize
with the grouping which would be based on the principle of continuity of gradation, that I
cannot entertain a doubt of its being the one on which (in our present state of ignorance
respecting the physiology of this tribe) our classification may be most securely based. For it
will be found that the several types of " porcellanous" Foraminifera, however diversified in
form, constitute a series connected throughout by the closest links of mutual affinity ; whilst
the proper " arenaceous" types form a parallel series, of which the members are not less
closely related to each other. In like manner we shall find that the far more numerous
forms of the " hyaline" Foraminifera may be ranked together into a small number of assem-
blages, the members of each of which are so gradationally united that the groups thus composed
are obviously in the highest degree natural ; whilst these series are at the same time connected
with each other, not only by their mutual approximation to certain fundamental types, but also
by intermediate forms which serve to link together even their more divergent portions, the
whole being thus united into a compact aggregate, of which there is no part that is not held
{as it were) to the rest by firmly cohesive attraction. — -It must not, however, be supposed that
every member of the one series is differentiated by the characters just enumerated from everv
member of the other. The non-perforation of the walls of the chambers, the singleness of
the septal partitions, and the freedom of the apertural communications between the chambers,
seem invariably to characterize the shells of the porcellanous type ; whilst the perforation of
the walls of the chambers, the duplication of the septal partitions, and the straitness of the
apertural communications, appear to be no less constant characteristics of the shells of the
hyaline type. The "intermediate" or "supplemental" skeleton, on the other hand, presents
itself to an extent that makes it readily distinguishable, only in the most developed forms of
the hyaline series ; and it is not a little remarkable that within the limits of one and the same
generic type {T/iio/joi7/s) we meet with certain forms in which this portion of the fabric is evolved
to an extraordinar)^ degree, whilst in others its presence is not to be traced at all. And the
same may be said of the " canal-system," which presents its most extensive and symmetrical
distribution in the highest examples of certain generic types, whose less elevated specimens show
scarcely any traces of it. Hence, whilst the presence of an "intermediate skeleton'' and of a
" canal-system" in one Foraminiferous shell serves to mark it as belonging to the higher section of
the hyaline series, their absence in another must not be regarded as indicating its porcellanous
characters, seeing that such absence prevails equally through the lower section of the hyaline
series also. And it is chiefly because their presence, in connection with other characters, serves
to mark a /iis/f>i or tendency in the one series, of which no trace whatever is presented by the
other, that it has been here included among the features of distinction between the two.

66. On the other hand, there is an entire absence of any other special relation between
the members of the " porcellanous " and those of the " hyaline " series, than that which
arises out of the configuration of their respective shells ; which configuration is determined b_v
their plans of (jrowtli, that is, by the direction in which new chambers are successively added.
Thus, in both series we have rectihneal, spiral, cyclical, and acervuline forms, with everv
gradation between these ; and it is true that such a striking isouiorpliisiii. displays itself between
certain types of these two series respectively, as would not unnaturally lead any svstematist
whose views of classification of Foraminifera might be founded on their supposed Molluscous

54 OF THE FORAMINIFERA GENERALLY:

affinities to a belief in their mutual affinity. A most complete isomorphism presents itself,
for example, in the simple spiral which constitutes one of the lowest forms of the porcellanous,
the arenaceous, and the hyaline series respectively ; and by such as have not traced out the
affinities of this spiral in each series, it might readily be supposed that such a conformity in
the plan of growth of the shell must be indicative of conformity in the physiological condition
of the animal.* But the porcellanous Cornuspira and the hyaline Spirillina differ not merely
in the texture of their shells, but in what we have seen to be the fundamental character of
non-perforation in the one and perforation in the other ; and whilst the former graduates
almost continuously into the spiroloculine form of Miliola, the latter is in like manner related
to Botalia through the vermiculate varieties of the latter genus. So the arenaceous, simply
spiral Trocliammina, which agrees with Conimpira in its non-perforation, not only differs from
it in the almost purely arenaceous composition of the shell, but also in the varietal forms into
which it passes ; and by some of these it is brought into relation with the other types of the are-
naceous series. — Passing now to the higher forms, we meet with so remarkable an isomorphism
between the nautiloid forms of Peneroplis and Operculina (the septa of the latter genus, besides
their regular aperture at the inner margin, being perforated here and there by secondary pores
that remind us of the former), between the subdivided spirals of Orbiculiiia and Heterostc^ina,
and between the discoidal OrbitoUtes and Cydoclyiwus, that, in any classification founded mainly
upon plan of growth, the genera of each pair must be placed in near proximity to each other ;
yet they are really separated by all those characters which have been shown to possess the
highest physiological value, and can only be regarded as " representing " each other in the
series to which they respectively belong. A like " representation '' will be shown to exist
among the higher forms of the arenaceous series ; certain varieties of Lituola, for example,
bearing a close resemblance to Nonionina, and others to the spiroline variety of Peneroplis ,•
whilst ValvuJina may take on the forms of Ttotalia, BuUuiina, and other hyaline Foraminifera.

67. It seems obvious, from the foregoing considerations, that the importance of plan of
growth, as a character available in the classification of Foraminifera, is far below tliat of the
aggregate of other characters which stand in more intimate relation to the physiological con-
dition of the animal ; and the low value which ought to be attached to it is further indicated
by its frequent tendency to variation within the limits of what are shown by the evidence of
gradational affinity to be well-marked natural groups. Such a tendency seems greatest in
the lower types of each series ; " polymorphism " being the rule among them, rather than the
exception. Thus we shall find that Niibecularia, one of the simplest of the porcellanous
Foraminifera, presents itself under such a variety of forms, that the attempt to classify these
in any system based on the geometrical arrangement of the successive segments, would
lead to nothing but a most absurd separation of what are clearly but varietal modifications of
one and the same type. In Vertebralina we find, with a closer general conformity to a
common type, a range of variation which is still very remarkable ; and even when we rise as

* Thus, by Professor Scliultze (xcvii, pp. 40, 41), the porcellanous and the hyaline spirals have been
ranked as Cornuspira jjlanorbis and C. perforata ; whilst by Prof. Williamson (cs, pp. 92, 93), the
porcellanous, arenaceous, and hyaline spirals are designated respectively Spirillina foliacea, S. arenacea,
and S, perforata.

PRINCIPLES OF CLASSIFICATION. 55

high as Peneroplis, we very commonly observe a change in the direction of growth from the
spiral to the rectilineal with the advance of life. The spiral growth of OrbicuUna, again,
often gives place to a cyclical plan exactly resembling that which is typical of Orbitolitcs ;
whilst at the commencement of the development of Orbitolites, which is typically cyclical, the
chambers are sometimes added according to a spiral arrangement. In the same manner, when
we enter upon the " hyaline" series, we shall find ourselves compelled by the like continuity
of affinities to rank as varietal modifications of the single generic type Nodosaria a long list
of reputed genera, separated by D'Orbigny under his three orders, Sfichostet/ues, Helicoste^ues,
and Enallosteyues : and marked changes in the plan of growth frequently present themselves
among the higher genera of that series in the life of one and the same individual ; the early
arrangement of the chambers of PlanorbuJina and Tinoporm, for example, being as typically
spiral as that which prevails in Bofalia, but flie additions being subsequently made in such a
manner as to convert the spiral, in the first instance, into a circular disk, which may then
increase at its periphery so irregularl}' that all definiteness of contour vanishes, whilst the
chambers may also be piled one upon another in an irregular " acei'vuline" manner, so as
entirely to mask either their original spiral or their secondary cyclical arrangement.

68. The foregoing examples serve to show, not only that neither plan of t/rowth nor
remdtant form can be rightly taken as a character for sepai-ating the great primary divisions
of FoRAMiNiFERA, but also that they are so often liable to variation within the limits
of genera, that no constant reliance can be placed on them as means of difl'erentiating even
these subordinate groups from each other. It will be usually found much safer, in fact, to
place our chief reliance on those characters which can be stated in terms of each individual
segment, than on those which can only be predicated of the aggregate. And no characters
are, in general, so free from the fallacy resulting from tendency to variation, as those which
are drawn from the nature and position of the septal apertures. Even these, however, in
certain exceptional cases, share in the general tendency to variation ; and in estimating the
value which should be attached to such diversities, it is important to bear in mind the remark
already made (p. 8) as to the purpose which is served by these apertures. It must obviously
be a matter of no great physiological importance, whether a number of those fine threads of
sarcode, which act as stolons connecting the successive segments of the body, and are put
forth as pseudopodia from the last, pass out in one undivided bundle, or be separated by the
interposition of minute pi'ocesses of shell, which convert a narrow fissure into a row of pores,
or a wide orifice into a cribriform plate. Such a difference exists between the aperture of
Rotalia and that of Calcarina, and between that of Miliola and that of Haucrina ; and it could
not be regarded as even of sub-generic value in those two cases, if it were not accompanied
by other distinctions. A far greater dissimilarity exists between the aperture of Feneroplis
and that of Bendritina, the former consisting of a linear series of separate pores, whilst the
latter is a single, large, dendritic orifice : and yet, as I have elsewhere shown (xv), the former
of these conditions graduates into the latter so continuously as to render it impossible to draw
any definite line of demarcation between them ; and each is related to the shape of the septal
plane, which may vary no less gradationally from that of a long, narrow band (Plate VII,
fig. 16, ff), to a cordate or sagittate form (figs. 6, a, 14, h, c), according to the compression or
turgidity of the spire. Hence, as there is a most remarkable accordance between these two

56 OF THE FORAMINIFERA GENERALLY:

types in all other respects, and their dififerences are such as occasionally present themselves
to a certain degree between the successively formed portions of one and the same organism,
they cannot be generically separated ; and, notwithstanding the extraordinary contrast
presented by their extreme forms, both in the shape of their septal plane and in that of their
aperture, the one must be regarded as merely a varietal modification of the other.

69. Since, then, even the characters which in some groups of Foraminifera are most
stable, are in others so inconstant as to be quite valueless for the purposes of the systematist,
the inquiry naturally arises whether any definite method of generic and specific differentiation
can be laid down; and to this inquiry I have to answer — not for myself alone, but for Messrs.
Parker and Rupert Jones, whose views on this point are in complete harmony with my own —
that in the present state of our knowledge such a methodization is impossible. Whether it will
ever be practicable to arrange the multitudinous forms of this group in natural assemblages
whose boundaries shall be capable of strict limitation, is to us by no means, certain ; since the
tendency of every extension of our researches is to enlarge our idea of the range through which
these forms may vary. And all that it seems to us at present feasible to attempt, is to group them
around certain generic types, each marked by some combination of characters which impresses
on it (so to speak) a distinctive physiognomy, and to trace out the principal modifications to
which these types are subject through the separate or combined variation of their characters.
Among these modifications there will generally be found some which indicate an afiinity towards
other types, so as to diminish the intervals between each type and those to which it is related.
Wherever such a gradation can be shown to exist with anything like complete continuity, its
presence will be accounted a suSicient reason for including the whole series (however
diversified in its extreme forms) under one and the same generic designation ; where, again, it
seems likely to be established by further research (which is sometimes especially the case in
regard to extinct types), the modification thus related will be ranked as a suh-c/enus ; while the
existence of such a decided break between any two types, as enables any specimen at present
known to be referred without hesitation (after a sufficient examination of its structure and
affinities) to one or to the other, will be held to justify their //ww/e separation.

70. The impracticability of applying the ordinary method of definition to the (/encra of
Foraminifera becomes an absolute impossibility in regard to species. For whether or not
there really exist in this group generic assemblages capable of being strictly limited by well-
marked boundaries, it may be affirmed with certainty that among the forms of which such
assemblages are composed, it is the exception, not the rule, to find one which is so isolated
from the rest by any constant and definite peculiarity, as to have the least claim to rank as a
nalaral species. Nothing is more easy, however, than to make artijiciaJ species in this group ;
for the variation to which every one of its generic forms is liable, gives rise to a multitude of
dissimilar forms most inviting to those systematists who consider that credit is to be gained
by adding new names to the already enormous list; and accordingly we find that a vast mass
of such specific names and definitions has been accumulated, of which but a very few really
express the facts they are designed to record. For it is the habit of such systematists
to pick out only what they consider the well-characterized types, and to disregard the inter-
mediate or osculant forms that establish the gradation between these, neglecting altogether

PRINCIPLES OF CLASSIFICATION.

57

the fact that the existence of such a gradational series entirely does away with the fundamental
assumption on which tlie idea of a natural species (as ordinarily understood) is based. When
a large collection of individuals of one generic type is brought together (such as that placed
in my hands by Mr. Gumming of the Opcrmlina of the Philippine Seas), it very commonly
happens that by selecting the most divergent forms, a considerable number of specific types —
say six, eight, twelve, or even twenty — might be readily establislicd, and a considerable part of
the collection might be arranged around these as centres ; but after all the specimens have
being thus separated, which present a sufSciently close conformity to those types to admit of
been referred to one or other of them without hesitation, there will remain a considerable
proportion in which the characters of two or more are combined with such equality as to
render it impossible to assign to them any other than an intermediate position, whilst there
will be others which present such departures from any of them as themselves to have an
equal claim to rank as distinct species ; so that there is no middle course between that
of grouping the whole series as varieties of one species, and that of erecting into a distinct
species every varietal modification presented by individuals, — a course which would be the
■reductio ad absurdum of the ordinary system of species-making in its application to this group.

71. Two sets of characters may be especially named, on which it has been customary to
found specific distinctions ; these are the form of the septal plane, and external sculpture or
stirface-markini/. Now, in regard to the first of these, it may be affirmed most positively
that wherever any marked variation exists, that variation will be found, on comparison of a
sufficient number of specimens, to be so gradational as to defy all attempts to use it as a
basis of specific differentiation. Of this we have a marked example in Operculina, six vertical
sections of which are shown in Fig. IX. Further, no dissimilarity between the form of the

Fig. IX.

e..

Vertical sectious of six specimeus of Operculina ; showing a remarkable diversity in tlie forms and proportions of the chambers

8

58

OF THE FORAMINIFERA GENERALLY :

septal plane in different individuals can be greater than that which often presents itself at
different periods of the life of one and the same individual. Thus, among tlie nauiiloid
Foraminifera, there is very commonly to be noticed a remarkable tendency to flattening- out
in the latest whorl ; the breadth of the spire being rapidly augmented, whilst its thickness
(or the space between its two lateral surfaces) is proportionally diminished. Of this, again,
we find a striking illustration in Operculina ; in which the attenuation of the last convolution

Fig. X

^.

Vertical section of the tluee outer convolutions of an Opcraihna, sliowing a complete change in the form and proportions

of the last convolution.

Fig. XI.

often proceeds to a far greater extent than in the example represented in the accompanying
fio-ure, the septal plane being thus converted in one turn of the spire from the form of a broad
arrow-head to that of a band so narrow as to be little else than a line, whilst it is
leno-thened in the same proportion. The form of the septal plane, moreover, is in direct
relation, not merely with the general contour of the shell, alike in its lateral and in its antero-
posterior aspects, but also with certain of its surface-markings. For if each chamber be
merely applied to the extremity of that from which it is budded forth, the whole of the
previously formed shell remains visible externally ; and thus, in the case of a nautiloid spiral,
all the whorls are traceable from its commencement to its termination. But it most commonly
happens that the earlier whorls are either partially or completely invested by the later:

where such investment is complete, nothing but the last whorl is
visible externally (Fig. XI) ; where, on the other hand, it is par-
tial, the earlier whorls maybe more or less clearly distinguished.
Now, the degi-ee of this investment is determined by the degree in
which the successive segments of the sarcode-body of the animal
send out lateral lobes that extend themselves over the previously
formed portion of the shell ; and this is manifested in the shell by
the development of what may be termed the alar prolongations
of the chambers, which are the portions formed to include
those lobes. Thus, in Fig. XII, we have an anterior view of
a nautiloid shell, in which the last whorl so little encroaches
on the preceding, that the septal plane s.p. terminates at the
an"-les h, h, which are but little nearer to the centre of the spire than the aperture a, which
lies against the margin of the preceding convolution. On the other hand, in Fig. XIII, we have
a like view of another nautiloid shell, in which the last whorl completely invests the preceding,

Lateral view of a nautiloid shell,
of which each convolution com-
pletely invests the preceding,
so that the chambers 1-S are
hidden bv 9-15.

PRINCIPLES OF CLASSIFICATION.

59

and the septal plane s.p. is here extended on either side into the " alar prolongations " a. p.,
a. p., until its angles h, h reach the umbilicus or centre of the spire. Now a difference of
this kind not unfrequently presents itself, •

not only between different individuals Fig. XII.

whose specific identity is demonstrated by
the gradational series that connects them,
but also between the different parts of one
and the same individual ; the latest whorl
often disengaging itself more or less com-
pletely, whilst each of the earlier whorls
was successively invested by that which
succeeded it. Hence it is obvious that no
such difference can be justly regarded as
a basis for specific distinction, until it shall
have been shown to be both constant in
its occurrence and uniform in its degree ;
the presumption being decidedly in favour
of its variability, until the contrary shall

have been established. It is in the genus Nummulites that the peculiarities in the
disposition of the alar prolowjations of the chambers, and of their intervening septa, seem
to have the greatest importance as differential characters, and have been most used for the
discrimination of species; but we shall find reason to question whether even there such
peculiarities have the uniformity and definiteness which are required to justify such an
employment of them.

72. Of surface-marUnfj there are two principal kinds, which are for the most part related
to the " porcellanous " and the " hyaline " types of shell-structure respectively. The surface
of the porcellanous shells, as already stated (t 57), is not unfrequently marked by striations
or by pittings, more or less conspicuous and regular in their arrangement ; and the value to
be attached to these must depend entirely upon the degree of constancy with which they present
themselves in each particular type. Thus in Vertehralina we shall find that the presence of
coarse striations, passing transversely between the septal bands (Plate V, figs. 17—25), is so far
constant in the first-formed portion of the shell (though very commonly wanting in the later
segments) as to afford important evidence in the determination of forms that might otherwise
be doubtful. So, again, the more delicate striation of PeneropUs (Plate VII, figs. 16, 18, 20)
is so constant and characteristic, that the exact similarity it presents in the " dendritine " and
" spiroline" forms (Plate VII, figs. 1,4, 12, 13, 21) becomes an important element in the deter-
mination of their merely varietal nature ; even its occasional obsolescence (figs. 2, 3) strengthen-
ing rather than weakening this conclusion, such obsolescence occurring after the same manner
in all these types. In MiUola, on the other hand, nothing can be less constant than the sculpture
which so remarkably distinguishes certain individuals (Plate VI, figs. 3, .5, 13, 14) as apparently
to justify their being ranked as well-characterised species ; for wherever a sufficient number of
individuals thus distinguished is brought together, there will be found some in which it is far
less conspicuous than usual, and others in which it is wholly wanting either on some part of

60 OF THE FORAMINIFERA GENERALLY :

the external surface or at some period of growth ; so that, a continuous gradation being thus
estabhshed between the most regularly sculptured and the perfectly smooth forms, it becomes
obvious that no valid specific distinction can be erected on such a basis in this type.

73. Among the "hyaline" shells, on the other hand, variety is given to the surface
marking chiefly by the interposition of bands or spots of non-tubular substance in the
midst of the tubular ; such portions being distinguished by their vitreous lustre from the
general surface, even when they do not project above it. Most commonly, however, they
are raised into ridges or tubercles ; and these are sometimes arranged with great regularity,
whilst in other instances they are extremely variable. Generally speaking, we find that when
either continuous bands or rows of spots of non-tubular substance repeat themselves with
anything like regularity in a direction trans vers/' to that of growth, these mark the position of
subjacent septa ; and, by the elevation of these septal bands, we have septal ridges or rows of
tubercles, such as are often strongly marked in the " cristellarian" type of Nodosaria (ex, PI. ii,
fig. 54), in Oppi-cuUna (Plate XVII, fig. 1), and in Cycloclypeiis (Plate XIX, fig. 2), But, between
these septal ridges, we often find a multitude of tubercular elevations ; sometimes arranged in
regular transverse rows, as in certain varieties of OpcrcuUna ; more commonly, however, with-
out any such symmetry, as in many Rotalia and TlanorbtdincB . These, instead of the vitreous
lustre, sometimes exhibit an opaque porcellanous whiteness (Plate XIII, fig. 15). In cases in
which the original walls of the shell are overlaid by subsecpient deposits, we very commonly find
that the size and prominence of these tubercles increase with every addition to its thickness ; so
that in section they present the appearance of cones whose base is at the surface of the shell,
whilst their apex points to its interior. This is often strikingly displayed in the umbilical
region of Opcrculhia (Plate XVII, fig. 1), and in the central regions of CydocJypeus (Plate XIX,
figs. 2, 5) and of Orbituides (Plate XX, fig. 2). The variability of any such ridges or tubercles,
however, is such as altogether to destroy their value as specific characters ; individuals in
which they present themselves under so pronounced and peculiar an aspect as to seem defi-
nitely differentiated by their presence from the ordinarj' type, being found to be connected
with it by a continuously gradational series ; whilst even on diff"erent parts of the very same
shell, the size, disposition, and aspect of the tubercles are found to vary so much as to render
exactness of definition altogether impossible.

m

74. Another kind of surface-marking in the "hyaline " series is given by ridges which
project from the shell, not transversely, but lonyHudinally, that is, in the direction of growth ;
these are very common in the genus Lagena (ex, PI. i, figs. 8-14), and in the protean forms of the
Nodosarian type (ex, PI. ii, figs. 36-48) ; but they are of no more value to the systematist than
those already noticed, since they vary greatly in the degree in which tliey are developed in
different individuals, and are frequently wanting on portions of shells which elsewhere present
them very strongly marked. The most remarkable modification of this kind of surface-marking
with which I am acquainted is the hexagonal areolation presented by certain " entosolenian ''
varieties of Layena (see ex, PI. i, figs. 29-32) ; ,this, however, is not more constant than the
similar areolation of certain varieties of Miliola, although it would at first seem to have more
value as a differential character on account of the difference of texture between the shell
substance of the ridges and that which forms the general surface. One other variety of

PRINCIPLES OF CLASSIFICATION. Gl

surface remains to be mentioned ; namel)% that hispid character which is given by the pro-
jection of conical spines from every part of it. Of this we have numerous examples among
the straight and slightly curved NodosaruB (Plate XII, fig. 2) ; whilst among spiral shells
we meet with it in the most pronounced degree in a varietal form frequently presented by the
young of Calcarina (Plate XIV, figs. 6, 7). The careful study which I have made of this last type
enables me to aflarra with confidence, that these conical spines are formed by an excessive
growth of the tubercles of non-tubular shell-substance already described, and that they usually
disappear with the advance of age, by an increase in the thickness of tlic ordinary shell
substance which fills up the spaces that intervene between them. And among the Nodusaria
they certainly have no more vahic as differential characters tlian the ridges already noticed.

75. Taking our stand, then, upon the characters by which the Order Reticularia is
difi"erentiated from otlier Rhizopods, — viz., the minute subdivision and the free inosculation
of the pseudopodia, the imperfect differentiation of the endosarc and the ectosarc, and the
absence both of nucleus and contractile vesicle, — ^we have finally to inquire how the group
thus constituted can be most naturally subdivided in accordance with the principles that have
now been laid down. At first sight, it would appear as if the groups of Gromida and
FoRAMiNiFERA Were so strong!)^ differentiated by the deficiency in the former of that
calcareous envelope which is the special characteristic of the latter, that they should constitute
two sections or sub-orders of corresponding rank ; and such a view has been adopted by
MM. Claparede and Lachmann (xxv, p. 34). If, however, we attach a greater value to
the characters furnislied by the animal than to those afforded by the material of its envelope
(and this appears to me the more natural method), we find that the affinity of the Gromida to
those Foraminifera whose shells, being imperforate, do not give passage to pseudopodia, is even
closer than is that of the Foraminifera having imperforate shells to those of which the shells
are perforated; whilst the systematic value of the difference in the material of the envelope
is lowered by the circumstance, that among the true Foraminifera we occasionally meet with
instances in which the only part of the shell that is really formed by an exudation from the
animal is the cement that holds together the particles of sand from which it derives its
solidity. Following out this principle, tlie whole Order Reticularia may be subdivided into
two primary groups, according as the envelope (whether membranous or shelly) is imperforate
or is perforated ; the pseudopodia in the former case issuing only from the single or multiple
aperture, whilst in the latter they proceed from the general surface of the body. The imper-
forate sub-order may be divided into three very natural groups, according as the nature of the
envelope is membranous, jjorcellanous, or arenaceous ; and thus we have the families Gromida,
MiLiOLiDA, and Lituolida. Throughout the perforated sub-order, on the other hand, the
texture of the shell is hyaline or vitreous, save in the few instances in which the ordinary shell-
substance is partially replaced by particles of sand ; and there seems no other l)asis for a
division of that sub-order into families, than that which is afforded by tiic mutual affinities
of its generic t3'pes.

The results of our inquiry up to this point, thei*efore, may be summed up as follows

.«

* Tlie nearest approach to the above principle of classification -wliich I fiud among preceding
systematists, is that hinted at, though not actually adopted, by j\I. Dujardiu (xxxvi). As the original

62 OF THE FORAMINIFERA GENERALLY.

Class RHIZOPODA, Order Reticularia.

Sub-order, imperforata.

Test membranous ..... Famil}' Gromida.

Shell porcellanous „ MUiolida.

Shell arenaceous ..... „ Lituolida.

outline of the system in which the Foraminifera first liad their true place assigned to them, the classi-
fication of M. Dujardin will always have an historical value, although its incompleteness has been
made apparent by subsequent researches. The Amihiens constitute the second, the Rhizopodes the
third, and the Actinophryens the fourth family of his Infusoria ; but as he distinctly states (p. 240) that
the structure of the animals is essentially the same in the first two cases, it is rather to be wondered
at that he should have limited the name Rhizopods to such as have the body enclosed in a testaceous
envelope. This envelope, he says, varies in consistence from a simple flexible membrane to a thick
calcareous shell, either solid or porous. But he does not regard these differences as equal in
importance to those presented by the form of the pseudopodial extensions of the sarcode-body,
according to which the group may be divided into two sections ; of which the first (corresponding to
Ehrenberg's family Arcellina) includes only the Arcella and Diffiugiw, whose pseudopodia are short,
thick, and rounded at their extremities, whilst the second comprehends all those whose pseudopodia
are filiform and much attenuated towards their extremities. This second section he subdivides into
three tribes ; the first composed of the genera Trinema, Euglypha, and Gromia (all discovered by him-
self), which are distinguished from Diffiugia only by the attenuation of their pseudopodia; the
second is composed of the single genus Miliola, which agrees with the ordinary Foraminifera in the
possession of a calcareous shell, whilst in having but a single large aperture from which the pseudopodia
extend themselves it corresponds with Gromia ; and the third includes the Foramimfera proper,
which he supposed to be all furnished with porous shells for the passage of pseudopodia from the
general surface of the body. It is remarkable how little change is required (and this rather in the
application of terms than in re-arrangement) to bring this outline into conformity with the more com-
plete system which subsequent research enables us now to frame. For if we extend the application
of M. Dujardin's term Rhizopodes not only to the Amibiens which precede them but to the Actino-
phryens which follow them in his classification, and transfer to the former from the central group the
genera Arcella and Difflugia whose animals are of the Amoeban type, and to the latter the genera
Trinema and Euglypha which are Actinophryan, we find the central group thus restricted to correspond
exactly with our Order IIeticulakia ; and the limitation or non-limitation of the pseudopodia to the
single or multiple aperture would probably have been adopted by i\I. Dujardin as the basis of his primary
divisions of that group, if he had been aware that Miliola, so far from being exceptional among Foraminifera
in this respect, is in reality the type of an extensive series. — Whilst this sheet is passing through the
press, I find that Prof Reuss has recently propounded to the Imperial Academy at Vienna (xci a)
a scheme of classification of which the principles are almost identical with my own. He considers the
composition and intimate structure of the shell to be characters of primary importance, and attaches but
little value in comparison to plan of growth. He still retains the distinction into Monoihalam.ia and
Polythalamia (which he terms Monomera and Polymera), but expresses himself doubtfully as to its
value.

CHAPTER IT.

OF THE FAMILY GROMIDA.

76. The members of the Family Gromida accord with the imperforate Foraminifera in
the characters furnished by their sarcode-bodj% M'hich puts forth its pseudopodial extensions
only from a single aperture ; but differ from them in having that body enclosed only in a mem-
branous test, which may be reduced to such tenuity as to be scarcely distinguishable. By
M. D'Orbigny this family was altogether ignored, no member of it having been known when
he first applied himself to the systematic study of the Foraminifera, and no mention havuig
been made in his subsequent writings even of its typical genus Groinia discovered by
M. Dujardin in 1835 (xxxv), notwithstanding the clear demonstration given by that
admirable observer of its close relationship to Miliola (xxxvi). Not less completely was
this type excluded by Professor Ehrenberg from his systematic arrangement of Bryozoa
(xl) ; the genus Gromia being apparently regarded by him as allied to Arcella and D'lJJlugia,
which he ranked as Infusoria. It was by Professor Schultzc (xcvii) that Gromia and its
allies were first introduced into a complete systematic arrangement of the Foraminifera ; but
he placed so much higher a value on the unilocularity of the " test " than on any other
character, as to associate them with Arcella and BiJjJugia, whose animals are of the Amoeban
type, with Trinema and Eughiplia, whose animals are Actinophryan in character, with Squamidina,
which has an imperforate calcareous shell of the Milioliue type, and with Orulina, whose shell
is perforated and hyaline, in the Family LagynidcB of his Monothalamia Testacea, — an
association which must be altogether incorrect if there be any truth in the principles laid down
in the preceding Chapter, as being those on which alone can any approach to a natural
classification of Foraminifera be founded. Between the " test" of Gromia and that of Arcella,
indeed, there is but little difference ; but between the animals which form and inhabit these
" tests" respectively, the difference is as wide as any that is known to exist in the whole
Rhizopod series ; and this difference has been cleai'ly recognized by MM. Claparede and
Lachmann (xxv).

Genus I. — Lieberkuhnia (Plate II).

77. This genus is the one of the whole Order Beticularia in which the envelope of the
sarcode-body is reduced to its minimum ; so that it approaches most nearly to the absolutely
naked condition, and may in consequence be most advantageously studied as a type of the
group, holding the same position in the Rcticulose series that Amccba does in the Lobose, and

64 FAMILY GROMIDA.

Adinoplirys in the Radiolarian. A detailed account of its very simple organization and of its
mode of life (so far as at present known) having been already given (^ 32), there is no occa-
sion here to repeat the description ; but it may be advantageous to point out that the origin
of the whole ramification of pseudopodial expansions from a single stem which is limited by
a definite envelope, shows Lieberkuhnia to be strictly conformable to the imperforate type.
From no other part of the body are pseudopodia given off, as would be the case if it had any
affinity to the perforated series.

Genus II.— Gromia (Plate III, fig. 2).

78. The genus Gromia was first constituted by M. Dujardin in 1835 (xxxv) for the
reception of a group of Khizopods characterised by the possession of a brownish-yellow, soft,
membranous, ovoidal or spheroidal " test," having a small round orifice, whence issue very
long pseudopodia, which ramify and become much attenuated towards their extremities. In
the membranous nature of its " test" Gromia resembles Arcella and Eii(jlyplia, but the character
of the animal entirely differentiates it ; and it thus holds in the Reticulose series a rank exactly
parallel to that oi Arcella in the Lobose, and oi Enr/li/jjlia in the Radiolarian. This genus has
since been especially studied by Schlumberger (xcix a); and still more recently by Professor
Schultze (xcvii), whose account of it is in some respects more complete than that of
Dujardin, but corresponds with his in all essential points.

79. The smooth, coloured "test" of Gromia, which commonly attains a diameter of
from 1-lOth to l-12th of an inch, looks to the naked eye very much like the egg of a Zoophyte
or the seed of some aquatic Plant ; and its real nature would not be suspected until, after an
interval of rest, the animal begins to creep about by means of its pseudopodia, and to mount
along the sides of the glass vessel that contains it. Some Gromia are marine, and are found
among tufts of Corallines, Ccramiacise, and other Alga3 ; whilst others inhabit fresh water,
and adhere to Ceratophylla, Confervae, and other plants of running streams. Various species
have been described, differing slightly in the size, form, and colour of the " test," and in the
proportional length of the pseudopodia ; but, with the evidence we have of the variability of
all such characters in other instances, these specific distinctions cannot be regarded as having
any valid claim to acceptance. The composition of the " test" has been studied by Schultze
(xcvii, p. 21), who states that it resists the action of boiling solutions of the caustic alkalies,
and that of the concentrated mineral acids, even sulphuric. With sugar and sulphuric
acid it gives a red colour ; whilst by iodine and sulphuric acid it is turned to a
blackish hue, with a tinge of violet. The organic substance which it seems most to
resemble in these reactions is cellulose, but it differs from cellulose in not being dissolved
by sulphuric acid ; and it would seem to have some relation to cJiitine and the
substance of the Iiorni/ tissues. Of the animal of Gromia, and of its mode of obtaining its
food, a sufficient account has already been given (^^ 33, 34) ; and it has only to be here
stated in addition, that the shell has no permanent attachment, but that the animal moves
slowly from place to place by the alternate extension and contraction of the pseudopodia which

GENUS LAGYNIS. 65

it projects in advance, those which it leaves behind it (so to speak) being retracted into the
general mass of the body, from which new ones are put forth in front.

Genus III.— Lagynis (Plate I, fig. 21).

79. It may be doubted whether this genus, first discovered by Prof. Schultze
(.xcvii, p. 56) in the Baltic sea in the year 1849, should be ranked as an aberrant type of
the family Gromida, or should be removed to the Adinoplirijan group ; the intermediate
character of its pseudopodian extensions, and the strong resemblance of its " test " to that of
JSurjlyjjha, being such as to justify either position. This " test," which seldom exceeds 1 -240th
of an inch in length, is unattached, membranous, transparent, and elastic, and has somewhat
the form of a retort with a prolonged neck and a large aperture. The sarcode-body rarely
fills its cavity, the posterior part of which is generally unoccupied save by four tapering pro-
longations, that come off from the hinder part of the sarcode-mass which occupies the central
part of the cavity, and extend themselves backwards so as nearly to meet each other at the
posterior extremity of the "test" (Plate I, fig. 21, .\). These processes, with the part of
the sarcode-body from which they proceed, are composed of a granular sarcode more
opaque than the rest; and this is disposed, in the middle portion of the cavity of the test,
around a bright globular centre. The anterior portion of the cavity, on the other hand, is
occupied by sarcode of peculiarly pellucid character ; and it is this which extends itself into
the pscudopodia that issue from the orifice. These pseudopodia, like those of the HHiculuria
generally, are very slender, in this respect contrasting very strongly with those of the typical
Ammham (though not unlike those of A. porrecta, fig. 18), but more resembling those of
certain Actinopliryans. They diverge and occasionally subdivide ; but do not extend to more
than two or three times the length of the shell; and they show little or no tendency to
reunite (as in Gromia), so as either to form a network or to establish fresh centres of ramifi-
cation. The sarcode-substance has not been seen to extend itself (as in Gromia) backwards
from the orifice over the surface of the test, so as to give off pseudopodia laterally and
posteriorly. Occasionally the sarcode-body is found to occupy only the posterior part of the
cavity of the test, and to present the form of a sphere without any prolongations, its bright
pellucid centre being still distinguishable in the midst of the darker substance (fig. 21, b).
Whether this retracted condition has any relation to the " encysted " state of Infusoria, is a
point still to be determined. It is pointed out by Prof. Sehultze that the " test " of
Lru/yiits hears a close resemblance to one described by Perty (lxxxii, Plate viii, fig. 21),
under the name of Eiyhipha currala, as having been found empty on the Simplon, at a height
of from 4000 to 5000 feet.

CHAPTER V.

OF THE FAMILY MILIOLIDA.

80. The series of generic types which is marked out by the porcellanous texture of the
shell {% 57), and by those other structural characters which are associated with that dis-
tinctive feature {%% 62 — 65), includes so great a variety both of modes of conformation and
of grades of development, that at first sight the association of all these into a single family
would seem altogether unnatural. As we proceed in our study of them, however, we shall
find that from the lowest to the highest of these forms each is most remarkably connected
with other parts of the series by links of affinity so strong as to forbid their dissociation ; so
that, starting from the humblest or simplest types, we are gradually conducted, with scarcely
any decided interruption, to the highest or most specialised. Thus in SquamuUna (Plate I, fig.
22) we have a raonothalamous shell, of which the shape, although not very definite, seems to
preclude any extension or super-addition. In Cornuspira (Plate V, fig. 1 6) we find that the shell,
although still remaining monothalamous or undivided, is indefinite in its mode of increase,
receiving a succession of increments which foreshadows the successional addition of new
chambers in the Polythalamia. From this undivided spiral to the regular, scarcely divided
spiral of certain " spiroloculine " forms of Mlliola, the transition is almost insensible ; from the
" spiroloculine" we pass by eas)' steps to all the other forms of the Milioline type; and certain of
the most aberrant of these establish the transition to Hauerina and Fahidaria, in which last the
Milioline type seems to reach its most complex phase, the cavity of the shell being minutely
subdivided, as in Orbiculina and Alveolina, and the single large orifice into being replaced
by multiple pores. Returning to our starting point, we shall find in the proteiform Nubecu-
Jaria (which seems as much related to SquamuUna as to Cornusjnra) a sort of primitive sketching-
out of the various plans of growth which are more perfectly evolved in higher parts of the
series ; all its forms, however, being obviously but varieties of one type, of which the most
definite positive character is afforded by the incompleteness of the separation between the
successive chambers. The substitution of the rectilineal for the spiralis more definitely mani-
fested (though still under a great variety of aspects) in Vertcbralina, and the division of the
chambers is more complete. From this we pass almost insensibly to Penerojjlis, which also
presents itself under the form of a spiral giving place to a straight line, and in which the
elongated fissure that constitutes the aperture in Vertcbralina is broken up into a row of
separate pores. The subdivision of the chambers of Peneroplis by secondary partitions con-

GENUS SQUAMULINA. 67

verts it into an OrbiciiUna ; and this, in the later stage of its existence, usually takes on the
cyclical mode of growth, whereby it is linked on to OrbitoKtes which ordinarily follows that
plan from the commencement ; whilst, on the other hand, the mere lengthening of its axis of
growth carries us from the discoidal Orhiculina to the fusiform Aheolina. The most peculiar
types at present kn6wn to belong to this series are Badylopora and Acicularia, which seem
to be formed upon somewhat the same plan as OrbitolUes, though separated from it by a
wider interval than exists elsewhere. — Hence we seem fully justified in bringing together
all these forms into a single Family, and in giving to this family a designation derived
from that one of its genera which seems most wideJij diffused both in space and in time, there
being none which can be regarded as typical in regard to form. The following tabular
arrangement of this family may assist in the appreciation of the relationships of its members.

FAMILY MILIOLIDA.

Squamulina.

I I

Nubecularia — Cornuspira.

I I

Vertebralina . . Miliola.

I I

Peneroplis . . . Hauerina.

I I

Orbiculina . . . .Fabularia.

I I

Alveolina Orbitolites.

I
Dactylopora.

I
Acicularia.

Genus 1. — Squamulina (Plate I, fig. 22).

81. The genus Squmitdina was instituted by Prof. Schultze (xcvii, p. 56) for a minute
monothalamion of which he found several specimens at Ancona, adhering to the surface
of Algae and to the side of a glass vessel in which sea-water had been long kept. The shell,
whose largest diameter is about l-.300lh of an inch, has the form of an irregular plano-convex
lens, being usually flat, or nearly so, on its attached side (which accommodates itself to the
surface whereon it grows), and convex on its free side, on some part of which — usually about
half way between the centre and the periphery — is a wide orifice from which the pseudopodia
issue. The shell is calcareous and opaque, and is destitute of pores ; its adherent layer is very
thin, and is with difiiculty detached from the surface to which it is attached. The substance
of the animal is of a brownish-yellow colour, as in Gromia ; its pseudopodia, however, seem
fewer and less disposed to subdivide and inosculate.

68 .FAMILY MILIOLIDA.

Genus II. — Cornuspira (Plate V, fig. 16).

82. Hisfori/. — The genus Cornuspira was instituted by Prof. Schultze (xcvn, p. 40), for
those calcareous-shelled Foraminifera which form a flat spire like that of a Planorbis, and
have their cavity simple and undivided ; and two species were distinguished by him, one
of them, C. planorbis, having the shell solid, the other, C. perforata, having it finely
porous. Prof. Williamson (ex, p. 91), whilst recognising both these forms, and describing
another in which the shell is arenaceous, reverted to the generic name Spiri/Ii/ia, which
had been previously given by Ehrenberg to a shell resembling Schultze's C. perforata,
and included all three forms under that designation ; at the same time changing the
specific name of Schultze's C. planorbis to adopt that of foliacea, which had been pre-
viously bestowed by Philippi upon a more advanced form of the same organism. Soldani
(by whom this shell seems to have been first figured), Philippi, Williamson, and Messrs. Parker
and Rupert Jones, have all recognised in its opaque-white porcellanous character a close
resemblance to that of the MilioUnce. This resemblance is unquestionable ; and if there be any
truth in the principles enunciated in the two preceding chapters, it is obvious that the imper-
forate porcellanous spirals and the perforated hyaline spirals must be regarded, in spite of
their almost exact resemblance in external form, as belonging to two fundamentally different
types. Reserving, therefore, the name Spirillina as the generic designation of the latter, I
concur with Messrs. Parker and Rupert Jones in thinking it expedient to make use of the
name Cornuspira as the distinctive appellation of the former.

83. External Characters. — The shell of Cornuspira is a simple flat spire, the suc-
cessive turns of which at first increase but slowly in width, but which at last opens
out rather suddenly, like that of many other Foraminifera growing upon the same type
(Plate V, fig. 16). The successive convolutions are in contact at their edges, but the later
do not extend themselves over the earlier, so that the whole of the spire remains visible
externally on each lateral surface. Not the least appearance of septal bands or constric-
tions presents itself at any part of the spire ; except that a slight depression may some-
times be detected, which marks ofl^ the primordial chamber from the spire that proceeds from
it. In the young form of this shell the tube is cylindrical or nearly so, and its aperture is
round ; but as it advances in age and flattens itself out, whilst the spire undergoes a rapid
increase in width, its two surfaces become so closely approximated that the form of the
aperture changes from a circle to a long, straight-sided fissure (fig. 1 6, a). The compressed
whorls of the adult often show a series of irregularly alternating ridges and depressions,
which cross the course of the convolutions with a convexity directed forwards, and these
seem to mark the successive additions which the shell has received. Occasionally, as in many
higher types, an abrupt narrowing of the spire takes place, so that the convolution is con-
tinued on the smaller scale of some previous portion of the whorl, as is shown in fig. 16.

84. Internal Structure. — The entire absence of septal divisions, indicated by the external
aspect of this type, is proved by an examination of its internal structure, which shows that
the cavity occupied by the sarcode-body of the animal is perfectly uninterrupted, except

GENERA CORNUSPIRA. AND NUBECULARIA. 6.9

where (as already mentioned) a slight constriction marks ofif the primordial chamber at the
commencement of the spire. Hence the body will present no appearance of segmentation
except at that point, and the large size of the external aperture will enable it to extend
its pseudopodia most freely into the surrounding medium. — The Cornuspira foliacea, which
is at present the only known form of this type, attains the diameter of l-8th of an inch.

85. Affinitlea. — In CornusjnrH we have a sort of rough sketch of the higher type of
helicine Foraminifera, which it greatly resembles in external form, but from which it differs
in the simplification of its structure resulting from the absence of segmentation in its sarcode-
body. Its growth, like theirs, is unlimited; and thus, although actuallj/ monothalamous,
it may be considered ixs /loteiilialli/ polythalamous (^ G2).

86. Geot^raphical and Gcolot/ical Distribution. — This type is at present very generally
diffused through various seas, its shells growing attached by one of their lateral surfaces
to Alga; and Zoophytes, usually at no great depth. It has not been met with in any
formation of older date than the Eocene; but it abounds in the "calcaire grossier," and
presents itself at every subsequent epoch.

Genus III. — NuBECUL.\RiA (Plate V, figs. 1 — 15).

87. Hislof!/. — The genus Niiheadana was first established by Defrance (xxix) for the
reception of an assemblage of small calcareous bodies of variable form and extremely indefi-
nite characters, which he found within univalve shells of the " calcaire grossier." He expressed
himself as altogether undecided in regard to the place to be assigned to them in the animal
series; but in figuring them he grouped them with Zoophytes (xxix, Zooph., PI. xliv, fig. 3).
A comparison of the figures given by him (imperfect as these are) with the figures previously
given by Soldani (ci) of certain of the bodies to which he gave the general designation Serpula,
serves to show that this type had been previously recognised by that painstaking observer.
The indefiniteness of Defrance's characterisation of the genus seems to have prevented its
adoption by subsequent authors ; thus we find that even Blainville did not accept it (vi a),
though retaining Defrance's figures and the name appended to them on the plate ; and
Lamarck makes no mention of it. The genus was entirely ignored by M. D'Orbigny, though
one of its multiform varieties was described and figured by him under the name Webhina riigosa
(v, PI. i, figs. 16 — ^18, and Lxxiii, p. 74, PI. xxi, figs. II, 12). It has, however, been noticed by
M. Dujardin (xxxviii), who remarks of it that its proper place is probably rather among Fora-
minifera than among Polypifera. The firm establishment and true characterisation of the genus,
however, can only be fairly attributed to Messrs. Parker and Rupert Jones, by whom it has
been especially studied in its recent as well as in its fossil forms (lv, p. 455), and who have
kindly furnished me with the materials on which the following account of it is based.

88. External Characters. — No Foraminiferous shells are more protean in shape than
those of Nubecularia, for we find them presenting almost every plan of growth that is to be
found among Foraminifera. It is one of their distinctive characters that they attach themselves
to other bodies, the surfaces of which they use as part of the walls of their own cavities ; and

70 FAMILY MILIOLIDA.

thus it happens that they mould themselves to the shape of the bodies to which they are adherent,
and that the plan of their own conformation varies accordingly. It is when growing on flat sur-
faces, such as those afforded by shells or sea-weeds, that Nubecularia best exhibit their characters
(Plate V, figs. 6, 13) ; when, on the other hand, they extend themselves over the projections of
fohated shells, or ensheath the stems and branches of Zoophytes, Corallines, &c., they often lose
all external traces of definiteness of plan (figs. 8, 9), and even their internal structure would
be unintelligible if the simpler forms did not supply the means of interpreting it. It is difiicult
to say what ought to be accounted the typical plan of conformation in this genus ; but as it
usually (though not always) commences in a sjjiral, which subsequently gives place to other
modes of growth, this may be conveniently adopted as the starting-point. The spiral shell
of Nubecularia differs from that of Cornuspira in several very important particulars. In the
first place, it is frequently deficient altogether on the attached side (figs. 1 — 3), so that the
cavity of the tube is there bounded only by the surface to which its edges are adherent, and
the form of its section is not circular, but semicircular. Sometimes, however, a layer of shell
is deposited on that surface, so as to close-in the tube (figs. 4, 1 1, 14) ; but this layer is so thin
as to require the support afforded to it by the surface to which it is adherent. On the other
hand, the -shelly substance of which the unattached side of the tube is composed is deposited
in unusual abundance, so as not only to form a very thick wall on the exposed surface, but to
fill up the grooves which would otherwise be left between the successive coils of the spire.
Thus it often comes to pass that the distinction between the coils is altogether obliterated,
and only from the general outline of the entire shell could it be supposed that a spire is
concealed beneath. This deficiency of shell on the attached side, with such an exuberant
thickness on its exposed side as masks its characteristic form, is observable not merely in the
spiral NubecularicB, but also in those curved, straight, zigzag, ramifying, and acervuline
varieties through which this generic type will be shown to range (fig. 9).

89. Internal Structure. — In those forms oi Nubecularia which spread themselves over plane
surfaces, the internal structure is readily disclosed by detaching the shell from its adhesion, and
looking at it from the under or attached side ; for its cavity is then either laid open altogether
(fig. 1), or becomes visible through the thin pellicle of shell which covers it (fig. 4). In the
most regular spiral forms the spire commences in a spheroidal chamber, from which it is
separated by a slight constriction, and it then rapidly opens itself out, especially in the second
or third whorl. Its cavity is partially divided at irregular intervals by imperfect septa, formed
by inflections of the walls of the tube, which curve inwards with a convexity directed forwards,
but stop far short of meeting at the axis of the tube, so that a wide aperture of communication
is left between the adjacent chambers. When the spire enlarges, a dilatation is seen beyond
every one of these constrictions, the narrowed aperture of one chamber being received, as it
were, into the dilated base of that which succeeds it (fig. 5). This is for the most part better
seen, however, in the ^//-ff^^/// growth (fig. 10), to which the spiral convolution very commonly
gives place after having made two or three turns ; the axis of growth alone being changed, and
the structure of the tube and its partitions remaining the same. This straight mode of growth
may prevail from the commencement, individuals sometimes presenting themselves in which
the spire is altogether wanting. Sometimes the new chamber is formed at the side instead
of in the axial hue of the preceding, so that the direction of growth is suddenly altered.

GENUS NUBECULARIA. 71

Sometimes, af^ain, a new chamber is formed at the side as well as at the end of the preceding, and
thus a branch may pass off at a considerable angle from tlie main axis (fig. 12). More commonly,
however, wlien such a lateral gemmation takes place, the new series of chambers which thus
originates advances along the side of the preceding (fig. 7) ; and by further offsets of the same
kind these parallel series may multiply to any extent, the new chambers sometimes arching
over those from which they are derived, so as even in these flat spreading forms to mark the
tendency to an acervuline aggregation. Furtlici-, the axis of growth may be neither straight
nor spiral, but may bend or twist in any direction ; the chambers still succeeding one another,
either in a single linear series, or in ramifying extensions, or in multiple rows ; and nothing
then marks the generic type save the texture of the shell, its attachment by one of its surfaces,
and the narrowing of the chambers behind the constrictions, followed by a dilatation in front
of them.

90. Instead, however, of extending itself in length, the shell not unfrequently widens
itself out so much, that the distance across the chambers is far greater than that which inter-
venes between the successive septa ; and it is then to be observed that, between each chamber
and the next, there are two or more apertures in the septum that divides them (fig. 15). This
plan of growth is carried to an extraordinary extent in the specimen represented in fig. 13, in
which the enormous increase in the transverse dimensions of the chambers is accompanied by a
great multiplication of these septal communications (fig. 14), so that a NiibeciiJaria formed upon
this type becomes a sort of rude sketch oi Penerojdis. In not a few cases, again, the growth takes
place almost from the commencement on the cyclical ^\n.xi (fig. 11), the first-formed chambers
extending themselves around that which is occupied by the primordial segment, and budding
off new chambers in all directions ; the successive chambers communicate with each other
laterally, as well as in a radial direction ; and thus a sort of sketch is presented of the plan of
growth characteristic of Orhitolites and Plunorbulina, to the lower forms of which last, indeed,
this type of Nuheeularia (the chambers of which I have always found to be much smaller than
the average) often presents a decided analogy.

91. Either of the foregoing modes of growth may give place to one in which no
regularity whatever can be traced, the successive chambers being no longer added on the
original plane alone, but piling themselves upon one another, without any discoverable system,
so as to imitate the acervuline growth which Planorbulina sometimes takes on. This is espe-
cially liable to happen with NuhccuJaricc that cluster around the stems and branches of
Corallines, Zoophytes, &c. ; and thus it comes to pass that, as already remarked, not only
does their external configuration become altogether amorphous, but their internal structure
seems to be entirely destitute of arrangement. By a careful comparison of the intermediate
forms, however, the true nature of these amorphous acervuline growths, as derivations from
the simpler and more regular types, is unmistakeably demonstrated. In the larger and
coarser acervuline specimens, it is not unfrequently to be observed that the surface is
roughened by the inclusion of fine particles of sand (which seem to be composed of commi-
nuted shell) in the proper calcareous substance of their shells ; but this substance is never
replaced by sand,, as in the truly arenaceous types.

72 FAMILY MILIOLIDA.

93. Affinities. — The type which has now been described is of no common interest, as
displaying the first nisvs of a Rhizopod towards the production of a multilocular shell, and as
marking out, though in a rude and indefinite form, the principal plans which are evolved with
much greater completeness and regularity in the higher types. Niibccularia is obviously
allied to Cornuspira on the one hand, and to Vertebralina on the other ; it cannot, however, be
said to be truly intermediate between those genera (though some of its forms approximate to
each), because it difi"ers from both of them in the deficiency of the shelly wall on one side, as
well as in the rude and almost amorphous aspect of its free surface.

93. Geographical Distribution. — The shells of this genus are, for the most part, inhabitants
of the warmer seas, being especially large and abundant in the Laminarian zone, in which
they sometimes attain the size of hemp-seeds, or even of split peas ; whilst, when brought up
from deeper water, attached to the shells of large Mollusks, they are much more minute.
They also occur in a detached condition, associated with other Foraminifera, in many recent
sea-sands from shallowish water.

94. Geoloyical Distribution. — Nuhecularia are abundant in some of the French Tertiaries,
have been met with attached to GrypliacB, &c., in many Oolitic Clays, and have been recog-
nised in abundance (though the examples were very minute) in the Triassic Clay of
Chellaston.

Genm IV. — Vertebralin.\ (Plate V, figs. 17 — 25).

95. Histori). — The genus Verlebralina was first characterised by D'Orbigny (lxix) in
1826 ; the name which he has assigned to it having been apparently suggested by the resem-
blance presented by some of its forms (Plate V, fig. 22) to the vertebral column of a Shark.
On account of its spiral commencement he placed it among his nautiloid Helicnslegues, though
admitting that its position there is anomalous (lxiii, p. 120). Its relationship to the
Milioline type was first clearly indicated by Professor Williamson (ex, p. 89), who has given
an excellent description of its characteristic form, and has very properly reunited with
Vertebralina striata, the V. cassis and V. mucronala, of D'Orbigny, the diiferential characters of
which are too slight and inconstant for their separation. He was not aware, however, of
the extraordinary poh/jnorphism which this type is found to display when the comparison is
extended through a sufficiently wide geographical and geological range.

96. External Characters. — The aspect of the shell in Veriehralinais generally opalescentand
brightly polished, and its surface is usually marked by delicate, longitudinal striations, which
have the strength of ribs in the thick-walled and more strongly characterised specimens, such
as D'Orbigny's V. mucronata (xcii, PI. vii, figs. 16 — 19), but which become obsolete, or even
disappear entirely, on the later portions of the more delicate and more aberrant specimens.
More rarely the surface is pitted. The shell is complete on both sides, and is usually a
symmetrically flattened tube ; it has no other attachment to the surface on which it grows, than

GEIMLS VERTIiBRALINA. 7:5

tliat afforded Ijy the sarcodc-ljody of the animal itself, ov by the gelatinous investment
of tlie sea-weed to which it adheres. Its growth nearly always eommences either in a regular
spiral or in a Milioline modification of it, each turn of the spire being commonly formed
(as in Hdiii'rina, *] 112) by three chambers, or more rarely (as in the ordinary MUiolee,
^ 1 04) by two ; and it was on certain forms which are at first strongly milioloid and
afterwards uniserial, that D'Orbigny founded his genus Arliculinn. The earlier whorls
of the spire are generally inclosed by those which succeed them ; but sometimes they are
merely surrounded by them, so that the whole of the spire remains apparent. The septa
are marked externally by depressed bands, which are not crossed by striations. After
making from two to four turns, tlic shell continues to grow in a straight line ; the succes-
sive chambers (usually to the uuml)er of five or six) being sometimes of extremely uniform
size, subcylindrical in shape, and disposed with great regidarity (fig. 22) ; whilst in other
cases they are progressively compressed, so that the shell becomes flatter and wider
(fig. 25) ; and they are sometimes disposed in a zigzag manner. In either of these cases, how-
ever, the type is very easily recognised by the form of the aperture, which is a simple fissure
with lips slightly everted, extending along the whole breadth of the septal plane ; and it is
further to be noticed that behind each septal plane there is a more or less well-marked con-
striction, after which the walls of the chambers open out again. These constrictions are some-
times marked in an unusual degree by the very sudden enlargement of the new chamber
formed beyond, as in the specimen represented in fig. 23. Sometimes, on the other hand,
the tendency to increase appears suddenly checked, the new chamber being considerably
smaller than that which preceded it (fig. 21), the dimensions of which are only again
attained after a progressive increase continued through several chambers. A similar teraporar)-
dwarfing has been already noticed in Cornnspira, and seems liable to occur in any type of
polythalamous Foraminifera.

97. Inlernal Sfrucftcre. — On laying open the shell of Vcrtchralhia, its cavity is found to
correspond very closely with its extei-nal contour, the walls of its chambers being everywhere
of very uniform thinness. The septal divisions are disposed at much more regular intervals
than in Nuhccularia, but still have rather the character of constrictions formed by an inflection
of the walls, than of regular partitions ; and the wide aperture in each septal plane can scarcely
be difl'erentiated from that of Nuhecularia, except in the somewhat patulous character which
it derives from the slight eversion of its lips.

98. Varieties. — The typical form just described is liable to a great modification in cither
of two principal directions. On the one hand the chambers may become nearly cylindrical
in form, and at the same time narrowed and elongated, so that the straight portion of the shell
is drawn out into the form of a rod (fig. 19), though still presenting its characteristic con-
traction and subsequent opening-out at each septum ; whilst the aperture from a narrow-
fissure becomes circular, or nearly so. This rectilineal elongation of the chambers may
extend even to the first-formed portion of the shell, the primordial chamber and its imme-
diate successors being uncoiled (as it were) into a series of long cylinders laid end to end in a
straight line, the striated and pitted surface of which, together with the occurrence of
intermediate modifications of form, mark their derivation from the ordinary type. On the other

10

74 FAMILY MILIOLIDA.

hand, the progressive -widening-out of the chambers may go on to such an extent as still
more to disguise the fundamental type, especially when they not only become extremeh'
elono-ated transversely, but even wind themselves round the edges of those previously formed,
so as almost to meet on the opposite side of the original spire (fig. 18). Even such an
extremely aberrant form of the one here represented, which was distinguished by Lamarck
(lix and lx) under the names Benulina and Benidites* (expressive of the resemblance of
its shape to that of a kidney), is distinctly recognisable as a modified Vertehralina by the
exact conformity of the first-formed portion of the shell to the regular type, and by the
characteristic form of its aperture, which is a fissure extending along the entire margin of
the last nearly circular chamber ; and, as already pointed out (^ 89), a similar tendency is
common in other typical forms of this division of Foraminifera. Arrests of development at
the spiral condition, sometimes producing a strong resemblance to Miliola, are not uncommon
in either of the varietal forms of Vertehralina (figs. 17,20); and it is thus that the broad
specimens distinguished by D'Orbigny (xcii, pi. vii, figs. 14, 15) by the name V. Cassis,
have been produced. A curious dwarfed example, from a depth of 360 fathoms in the
Mediterranean, is represented in fig. 24.

99. Affinitief;. — It is obvious that Vertehralina may be considered as an advance upon Nuhe-
cularia, alike in the symmetrical conformation of its shell, and in the more definite plan of its
o-rowth. In that early condition in which it is sometimes arrested, it presents a close afiinity
to the MilioUne type ; whilst its compressed and especially its reniform varieties bring it into
close relationship to Peneroplis, which it often strongly resembles in shape, being always distin-
guishable from it, however, by the nature of the septal aperture, and generally also by the
inferior lustre and opalescence of the shell.

100. Geograpldcal Bistrihution. — Although specimens of Vertehralina are occasionally met
with among the Shetland islands, yet there is strong reason to believe that they have been trans-
ported thither from some warmer region ; as this genus seems, like Peneroplis, to belong
properly to tropical and sub-tropical seas, through which it is pretty generally diffused,
although in far less abundance than Peneroplis. '

101. Geological Bistrihution. — This genus presents itself in various Tertiary deposits ;
and it is from these that its most aberrant forms are supplied, although approximations to
them are furnished by their existing representatives.

Genus V.— Miliola (Plate VI, figs. 1—33).

103. History. — The generic term Miliolites was applied by Lamarck (lviii) in 1804 to
certain fossil forms belonging to a very common type, of which examples had been noticed
by LinnEeus (lxiii) as Serpula seminulum, by Soldani (ci) as Frumentaria, and by Montagu
(lxv) as Vermiculum; the designation having been apparently suggested by the resemblance

* These names are erroneously cited by Prof. Williamson (cs, p. 44) as synonyms of Peneroplis.

GENUS MILIOLA. 75

to millet-seed borne by the minute bodies to which it is applied. The Lamarckian genus was
adopted by various subsequent writers ; its name being modified to 3Iilio/rt or Miliolina for
the purpose of including the recent forms, which diifer in no essential particular from the
fossil. But in M. D'Orbigny's first systematic ari'angement of the Foraminifera (lxix) he
broke up this genus into the genera Uniloculina, Biloculina, Triloculina, Quinquelocidina, Sjpiro-
loculina, Adelosina, and CriicilocuUna ; and these he associated with Sjiharoidina (of which the
examples he cites as typical are really allied to Glohii/erinn, having a perforated hyaline
shell), and Articidina (which is in reality a varietal form of Vertcbiyi/lna, ^ 90), into his Order
AgathistivGUES ; his definition of which might have served as the generic character of
Miliula, if it had been founded on a correct conception of its typical structure. To the fore-
going genera, D'Orbigny subsequently added Fabularia (at first wrongly placed by him else-
where), a type which will hereafter be shown to present a peculiar development of the Milio-
line (1 116). Our reasons for reuniting the first seven of the genera just enumerated, with
all their multitudinous species, under the single type Miliola, without attempting to establish
even specific differentiations, will presently become apparent. With regard to his generic
divisions it is not a little singular that M. D'Orbigny should have remarked as follows : —
" We tliink it diflicult to find genera more distinct one from another than are those of this
Order. They present forms so sharply defined, that there really exists no transition between
them; and thus any one by a few liours' study will always find himself able to distinguish
them " (lxxiii, p. 256). Now although a few hours' study, prosecuted after the fashion of
M. D'Orbigny, may lead to an acceptance of his generic and specific distinctions as valid, yet
in precise proportion as that study is prolonged, and is made to include a sufiiciently large
number of examples of this type, brought from all the seas and from all the geological deposits
in which it occurs, do its results pi'ove to be of quite an opposite character. For the types
which were represented by M. D'Orbigny as so sharply defined, are found, on careful compa-
rison — as has been shown by Mr. W. K. Parker (lxxv) on whose view of tliis genus my own
account of it is based — to graduate into one another so insensibly, that no line of demarcation,
either specific or generic, can be drawn between them; so that no middle course can be
adopted between ranking them all as varieties of one species, distinguished by the degree
and direction of their divergence from a central type, and multiplying almost indefinitely
the number of species by adopting the most trivial modifications of form or surface-marking
as differential characters. This truth has already been partly apprehended by Profs.
Schultze and Williamson ; the former of whom (xcvii) has reunited the genera Trilocidina
and (luinqudocuHna under the generic designation Miliola ; whilst the latter (ex) has brought
them together under the name Miliolina, with the addition of Adelosina, which he rightly
states (p. 89) to be nothing else than a young form of the same type, distinguished by the
peculiar retort-shape of the primordial and the next succeeding chambers. Prof. Williamson
truly remarks (p. 80) that "none of the Foraminifera are more liable to variation than those
comprehended in the Lamarckian genus Miliolitcs ;" and adds (p. 87), that some of his "most
able correspondents, who previously thought that the species of Miliolinm ought to be made
much more numerous, on endeavouring to group the specimens in their cabinets according
to such views, found their difliculties increase with the multiplication of their specimens."

103. External Characters and Internal Structure. — The essential plan of conformation in the

76 FAMILY MILIOLIDA.

whole Miliolinc series is so simple, that it may be readily apprehended from a survey of the
external features of its fundamental type. Yet these features are liable to be so completely
masked, as altogether to lose their chai-acteristic aspect ; and since there hence arises so com-
plete a want of agreement between external characters and internal structure, as leads to the
entire misapprehension of the latter if too exclusive confidence be placed in the former,
it seems desirable to study both together in such a manner as to bring out their true relations.
And in this way we shall come to perceive the fundamental unity which prevails through a
range of varietal modifications so wide, as at first sight to appear to justify the creation of
an almost unlimited number of genera and species.

104. The fundamental " idea" of a MiJiola is best displayed in such a form as that
represented in Plate YI, fig. 1, which shows but little departure from the continuous spiral of
Cornusjjir'i ; the diifcrence consisting chiefly in this, — that each turn of the spiral is interrupted
at two opposite points by a constriction followed by an enlargement : and that, as the inter-
ruptions in successive turns are always at the extremities of the same diameter, the whole
spire is made up of a series of half-turns arranged symmetrically on its two sides. Each of
these half-turns is larger than that Avhich preceded it, but its dimensions scarcely change
between its two ends; so that the increase in the diameter of the tube is not gradual, but
takes place at successive intervals, each chamber being not only longer than its predecessor
on the opposite side, but also larger in sectional area. The form of that area departs from
the circular, in consequence of the tendency which each turn of the spire has to extend itself
in some degree over the preceding. Although this extension is but slight in the example we

. are considering, it is enough to give a concave instead of a convex border to the inner
wall of the chamber; which inner wall is, in fact, nothing else than the outer wall of the pre-
ceding turn, the shelly tube of the new chamber being there incomplete (^ 62). The
aperture of the last chamber is somewhat constricted : and it is further encroached-on bv
a tongue or tooth-like projection of shell substance from its inner margin (figs. 16 — 18) ; this
pi'ojection, which may be conveniently termed the " valve," varies greatly in size and form,
but when most developed, it converts what would otherwise have been a free nearly circular
passage into a comparative!}' narrow cresccntic slit. A similar " valve," whicli may be regarded
as a rudimentar}' septum (^ 109), exists at each of the constrictions that marks the division
of the chambers.

105. It is comparatively rare, however, to find so slight a departure from the regular
spiral plan, as is shown in specimens of the kind just described. For in by far the larger
number of cases, the diameter at the two extremities of which the septal constrictions occur
is more or less elongated ; and this elongation may proceed so far as to give it twice the
length of the transverse diameter (fig. 2), thus substituting for the spirality of the original
type an apparently Uhiicral arrangement, which has caused D'Orbigny and his followers to
define the Miliolinc group as if the shell were composed of " chambers clustered ='■ on two,
three, four, or five faces of a common axis.

* For the word pelototmees, \Tliich is intended to indicate the kind of aggregation produced by
■winding a ball of cotton, there is no proper equivalent iu our language.

GENUS MILIOLA.

77

Diagvaiiiiuulic ie(jrcscii-
tation of tlie Animal of

Hence it is ob-

106. The conformation of the sarcode-body of the animal obtained by the decalcification
of the shell, exactly corresponds with what the characters presented by its envelope would
lead us to anticipate. Starting from the ordinary primordial segment

(Fig. XIV, o), we find this giving origin, by a constricted neck or lu;. XR.

"stolon," to the first longitudinal segment 1, which doubles round one
side of it, and is then again constricted into a " stolon ;" from this pro-
ceeds the second longitudinal segment l', whicli passes round the other
side of the primordial spheroid, and, liaving extended itself beyond the
first, narrows itself at the opposite end of the diameter into a stolon ; from
this proceeds a third longitudinal segment 3, whicli passes round the
first and extends beyond it, giving origin, by a constricted stolon, to a
fourth 1, which in like manner passes round the second and extends
beyond it ; and this mode of increase may continue until a considerable
number of segments have lieen formed on either side of the primordial
spheroid, the last extending itself into pseudopodia at its termination,
vious that each segment grows in a direction contrary to that of the segment which
immediately preceded it, but corresponding to that of the ante-penultimate ^segment;
and that the pseudopodial extensions will be put forth alternately from one and the other
extremity of the body. And it is further obvious that this Milioline type involves, so
far as the structure of the animal is concerned, no more considerable departure from the
simple type of Coriui^piva than that which is produced by the narrowing of the spire as it
crosses each end of its long diameter, — a conclusion which derives additional support from
tlie exact conformity to the Coniuxpiru type, whicli, as already shown (^ 49), is presented bv
the young oi j\liIioIa (see xcvtt, plate ii, figs. 1 — 6).

107. The cliaractcrs adopted by D'Orbignv for the differentiation of his genera are for
the most part furnished by the number of chambers which show themselves externallv : a
variation whicli depends upon the degree in which the later chambers invest the earher, upon
the symmetry of their shape, and upon the mode in which they arc disposed with reference
to the diameter of tlie spire. Thus if the successive segments simply increase in diameter
without departing much from their primitive cylindrical
form, so that the successive chambers of the shell merely
apply themselves to the external surfaces of those which
preceded them, then the whole series of chambers is visible
on each side of the adult slicll ; and the ^fJIUdu which
grows upon this plan, wliicli will be readily understood
from the ideal transverse sections shown in Fig. XV,
is distinguished as Spiroloculina (Plate VI, figs. 1, 2). If,
however, the segments of sarcode extend themselves on
either side into " alar lobes," and these are symmetrically
prolonged so as completely to cover each side of the cham-
bers to which they are applied, as shown in Fig. XVI,
then only in-o chambers — the last and the penultimate —
are visible externally, and we have a Wdoadma (Plato VI. fig. 7).' It often happeu-

FiG. X\

Idi'al transverse sections of Spli'ijloadl-uf.

78

FAMILY MILIOLIDA.

however, that the alar lobes of one side are more prolonged than those of the other, so that
more of the earlier chambers of the shell are shown on the one face than on the other ; in this

Fig. XVII.
A.

B.

C.

Ideal transverse sections of Bilocnlina.

Ideal transverse seel ions of Qiii».queloculina.

way it often comes to pass that fice chambers are visible externally on one side of the shell,
whilst only three are apparent on the other (Fig. XVII) ; and this type is the Quinqudoculina of
D'Orbigny (Plate VI, figs. 3 — G). It is, however, subject to great inconstancy as to the
number of chambers visible externally ; this being usually from fJiree to citjld on one side, and
from lico to (six on the other ; some shells formed on this plan having only tivo chambers visible
on one side and three on the other.* A greater departure from the ordinary mode of growth,
however, is shown by those Miliolm in which the alternation in the direction of the successive
segments of the sarcode-body is not duplex but triplex ; so that the chambers of the shell,
instead of lying on the two sides of the diameter of the spire, cluster around it (so to speak)
triangularly, as shown in Fig. XVIII ; thus causing the shell to become three-sided, and ren-

FiG. XVIII.

Ideal transverse sections of Triloculina.

* It was from having perceived the unimportance of these numerical variations in shells formed
on the plan above described, that Profs. Schultze (xcvii) and Williamson (ex) were led to reunite

GENUS MILIOLA. 79

dering three chambers always visible externally- This is the true Triloculine form (Plate VI,
figs. 13, 14).

108. Now although, if typical specimens only Avere compared, these characters might
well seem to be sufficiently definite to justify the generic differentiations which have been
founded upon them, yet the comparison of extensive suites of specimens brought from
different localities shows that they are subject to an inconstancy whicli altogether destroys
their value. And this inconstancy is readily accounted for, when due allowance is made for
the indefiniteness in the form of the sarcode-body of the animal ; since, as we have seen, it is
dependent upon the degree in which the " alar lobes" of the new segments extend themselves
over the surfaces of the preceding chambers, and on the equality or otherwise of the pro-
longations on the two sides — characters which are extremely liable to variation among
Foraminifera. Of those subordinate departures from the typical form of the segments, whicli
convert their ordinarily rounded outline (Figs. XV, a ; XVI, a, b ; XVII, a ; XVIII, a) into
a carinate or angular contour (Figs. XV, b, c ; XVI, c ; XVII, b, c ; XVIII, b) — differences
on which a vast multitude of specific differentiations have been founded — it can only be here
stated generally that they are subject to the same uncertainty as the larger ones already
disposed of.

109. With such diversities in the form of the chambers are associated corresponding
diversities in that of the apcriure ; which may be elongated laterally so as from a circle tc
become an oval (which is sometimes narrowed into a mere slit), or may approach the form of
a square (Plate VI, figs. 8 — 12, 16 — 33). The shape of the "valve," again, varies with that
of the aperture, and has further variations of its own. In the MUiola cydostoma of Schultze
(xcvii, plate ii, figs. 14, 15), the valve is altogether wanting, and the aperture is quite round.
In the Spirohculina represented in Plate VI, fig. 1, the aperture, shown in fig. 16, has but a
very small projection ; this projection is a httle larger in the specimen represented in fig. 2,
of which the aperture is shown in fig. 17, and is somewhat extended laterally; and in the
QiiinquelocuUna represented in fig. 3, of which the aperture is shown in fig. 18, the valve is
distinctly bifid. In Bilocidlna the usual form of the "valve," as shown in figs. 7, 8, 10, 1 1, 12,
is that of a broad, rounded tongue, springing from the whole of one side of the aperture ; but
in the specimen shown in fig. 9, the valve, still much extended laterally, springs from a nar-
rower base. In figs. 1 9 — 32 is shown a very remarkable series of apertures and valves of a
large MUiola, from specimens brought by Mr. Cuming from the Philippine seas ; of which
variety an example is represented in fig. 33 broken open, so as to show the interior of the
last chamber, and to allow its aperture and valve to be seen from within, whilst the much
smaller aperture and simpler valve of the penultimate chamber are seen from without. This
series is particularly interesting, as showing the wide range of variation that exists in regard
to the form both of the aperture and of the valve, among a number of individuals whicli
must unquestionably be regarded as belonging to the same species ; some of the widest

QmnquelocuUna and TrilocuUna . Neither of them, however, seems to have apprehended the essential
peculiarity of the real Triloculine type to be next described, although this had been correctly pointed
out by M. D'Orbiguy.

80 FAMILY MILIOLIDA.

divergences being presented at the apertures of the successive chambers of one and the same
individual, as seen in fig. 33. In no two are the valves exactly alike in form ; and yet it is
obvious throughout that they are constructed (so to speak) upon the same model. They all
possess, in a more or less developed condition, a vertical plate or keel, which rises fi-om the
median line of the horizontal part of the valve ; and this keel, as is seen in the oblique view
given in fig. 30, frequently forms a sort of arch hollowed beneath like a bridge. In fig. 28
Avill be noticed a remarkable development of two pi'ocesses from the projecting angles of the
aperture, which are seen in a rudimentary condition in several other figures. In fig. 31, the
valve is so much extended horizontally, and the aperture is so unusually contracted, that
what should be the free margin of the valve has come to coalesce completely in one part, and
nearly to do so in another, with an ingrowth from the margin of the aperture ; thus distinctly
tending towards the formation of a complete septum perforated with separate pores, such as
we find in certain other modifications of the 3Iilioline type (•[■[ 110, 111, 118).

1 10. A more remarkable departure from the ordinary type of aperture than any of the
preceding, is presented in the CrucilocuUiw o{ D'Orbignj'; which is a well-marked " triloculine"'
Miliola (fig. 15), of which the aperture has (so 40 speak) four small valves instead of one, a
crucial fissure being left between them. This extreme variety is very rare, being only known
to occur in the coast of Patagonia ; but approaches to it arc met with elsewhere. Another
remarkable departure from the ordinary type of aperture is occasionally found in the well
known " quinqueloculine " Miliola of the Grignon tcrtiarics (the MiHolHe>< mivoriai/ of Lamarck,
the QiniiquelocitHna saxorinii of D'Orbign}'), the \\ alls of whose chambers are often so thick as
to leave but little space for the sarcode-body, which is further encroached on by ridges that
project from their inner surface ; the aperture is much contracted and its " valve "' small ; and
sometimes the internal ridges, coming up into the aperture and coalescing with the valve,
form a cribriform septum that seems to foreshadow that of Faljidaria (to which type this

, variety presents an obvious tendency) and of Peneroplis. We shall presently see that a
more perfectly-developed cribriform aperture is one of the principal features of the sub-
genus Haueriiia.

111. Not less variable in this genus is the surface-marking of the shell ; for, although
normally smooth and sometimes highly polished, it often presents a scabrous aspect, and is
sometimes marked by a more or less regular pattern, formed either by longitudinal ribs as in
Plate "N'l, figs. 3, 4, 33, by transverse plications extending to the interior of the chamber as
in fig. 5, by minute pits arranged in longitudinal series as in fig. 14, by a honey-comb
areolation as in fig. 13, or by various modifications and combinations of these plans. Now
although such well-marked specimens as the four here figured might be reasonably considered,
if taken by themselves, as distinct specific types, yet the comparison of a sufficiently large
number of individuals necessitates the abandonment of any differentiation founded upon the
characters they respectively present ; for it is shown by such comparison that all these kinds
of ornamentation shade off so insensibly into the smooth and pohshed surface of the ordinary
Milioline shell (a specimen which is pitted or ribbed on one part of its surface being often
smooth on another, and this without any appearance of having been subjected to attrition),
that no use can be made of them as specific characters. Thus in the thickest-walled examples

GENUS MILIOLA. 81

of the MUlola m.rormi/ mentioned \n the last paragraph, the external surface is often marked
by extremely deep circular pits ; but these are not usually found on the outer walls of the
earlier chambers of the very same specimens, and a gradational series of specimens may be
easily selected which should show an insensible transition from the most deeply pitted to the
most perfectly smooth individuals. Sometimes the shells of Miliolce, especially of the " trilo-
culine " and " quinqueloculine " varieties, acquire an arenaceous surface (fig. 6) from the
imbedding of grains of sand in the ordinary calcareous substance of the shell previously to
its solidification. These " arenaceous" individuals vary greatly in appearance, according to the
size and character of the particles of the sandy material forming the sea-bottom in their
respective localities.

112. Affinities. — It is obvious from what has been already stated (^ 104), that the
relationship is very close between the least specialized of the " spiroloculine" forms of Miliola
and the ordinary Cormtspira. Again, not only do certain varietal forms of Vertebralina
very closely approximate Mi/iohc in their mode of growth, but Miliola occasionally takes on a
uniserial plan of increase resembling that of Vrrti'hraJina ; so that individuals not unfrcqucntly
present themselves in which the presence or absence of a " valve" is the chief diagnostic
character ; and even this, as we have seen (^ 109), cannot be relied on as a constant differen-
tiation of these two genera. With Feneroplis, again, the Milioline type is connected by a very
interesting modification which has received from D'Orbigny the generic designation Hauerina;
this designation it will be convenient for us to retain as that of a sub-genus of Miliola (with
which it is obviously most intimately connected), without attempting to define the precise degree
of relationship of the two. The real character of Hauerina was completely misapprehended
by D'Orbigny, who, misled by the spirality of its growth (in its early state, at least), placed
it (lxxiii, p. 118) among \\is HelirositY/ucs, between OjjerciiUna and Vertebralina, to the latter
of which it is truly allied, whilst from the former it is separated by as wide an interval
as can exist among any two types of Foraminifera. In the young state of Hauerina, the
cornu^piral form which Miliola generally present in the first instance (^ 106) is retained
longer than usual ; but a distinct division into chambers shows itself in the passage to adult
age ; and as three or (less frequently) four chambers form the circuit of the outer whorls,
the shell has a three- or a four-sided contour (Plate VI, figs. 34, 36). The aperture, like that
occasionally presented by Miliola mxornm, is cribriform (fig. 36, b).* Although described by
M. D'Orbigny as only existing in a fossil state, this type occurs at the present time in the
Indian, Australian, and other tropical and sub-tropical seas. The external surface of its
shell is sometimes smooth, sometimes delicately striated (fig. 36, a) ; whilst sometimes its
walls are very deeply plicated transversely (fig. 35), — a varietal modification of which
we have already seen a less strongly marked example among the ordinary Miliohe (fig. 5).

113. By the Miliola saxoriun, again, the Milioline type is obviously brought into close

* In the description and figure of H. compressa, given by D'Orbigny (lxxiii, p. 119, pi. v,
figs. 26, 27), the septal plane is represented as perforated by a single small, oval aperture, surrounded
by several large, granular elevations ; but these (as appears from the examination of recent specimens
of the same type) really mark the place of passages which have been filled by fossilization.

11

S_> FAMILY MILIOLIDA.

relationship ^vith Fabularia, the pecuharity of whose structure consists in a higher develop-
ment of that tendency to subdivision of the general cavity of each chamber, of which M.
saworuiji presents a rudimentary manifestation. Through T'ahtlaria, again, the Milioline t}'pe
will be seen to be related to AlvcoRna, Orhiculvna, and Orhitolileii, all of which are characterised
by the like subdivision ; and it is most interesting to trace in some forms even of the highly
specialized OrbitoJites a return, as regards the conformation and aspect of the primordial
chamber and of that which immediately succeeds it, to the t}'pe presented by the corre-
sponding portion of an ordinary Miliola.

114. Geographical Distribution. — Probably no Foraminifera are at present more
universally diffused than those of the Milioline type, which are most abundant between the
shore and a depth of 150 fathoms, but occasionally present themselves among the products
brought up from deep-sea soundings. The largest and best developed forms of this tj^pe,
such as that represented in fig. 33, are from the littoral zone of tropical seas. The shell is
itself perfectly free ; but the sarcode body of the animal by which the shell is usually invested
during life attaches itself to sea-weeds, zoophytes, &c., to which Miliola may often be found
adherent.

115. Geological Distribution — The J/?72o/2Me type may be traced back in geological time
as far as the Lias, being rather abundant in the clay of that period from Stockton in
Warwickshire ; it is there, however, very small and delicate, presenting a condition exactly
analogous to that of recent forms brought up from depths of from 350 to 500 fathoms. It is
constantly present in the Gault, retaining its small dimensions, and also in the Chalk marl.
From the upper Chalk to the present period it is everywhere abundant in marine deposits,
having accumulated in certain parts of the Eocene period to such a vast extent that certain
beds of the " calcaire grossier" are almost entirely composed of aggregations of M. saxoruiii,
and are known as "Miliolite limestone."

Genus VIII.— Fabularia (Plate VI, figs. 37,38).

116. History. — The genus Fabularia was first distinguished by Defrance (xxix), who
applied that name to a body having a somewhat bean-like form, which occurs fossil in the
Paris Tertiaries, and which he had pre\aously confounded with Alveolina. He was, however,
totally ignorant of its real nature ; and it is now somewhat amusing to find him suggesting
that, as the irregular pores of its interior could not have contained polypes, it was probably
an internal shell enclosed like the " cuttle-fish bone" in the body of some Mollusk. Its place
as one of the Foraminifera was first indicated by D'Orbigny (lxix) ; but not being then
acquainted with its real structure, he grouped it among his Entomostegues. Subsequently,
however, he was led by more careful inquiry to perceive its essential conformity to the
Milioloid type, and to group it among his Agathistegues (lxxiii) ; and he correctly states that
it is most nearly related to Biloeulina, its difference consisting in this — that the cavity of each

«

GENUS FABULAEIA. 83

chamber, instead of being an empty space, is partly occupied with soUd shell-substance,
which is so disposed as to divide it into a great number of capillary tubes, whilst its aperture,
instead of being single, is made up of numerous minute pores.

117. External Characters. — The general aspect of Fabularia (Plate VI, fig- 37, a, b)
so remarkably resembles that of a gigantic BUumlina, as to occasion some surprise that the
true relationship of this type was not earlier recognised. In fact, it externally differs only in
size, — often attaining a length of 0'24 inch, and a breadth of 0-18 inch, thus far exceeding
the largest Mlliu/ce in dimensions, and in the cribriform character of its aperture, in which
it agrees with //««mH« (f 112). Very commonly, however, the peculiar structure of its
interior is partly disclosed by the abrasion of the surface, which lays open the superficial
series of the longitudinal canals into which it is divided.

118. Infernal Structure. — The internal structure of Fabularia may be made out very
tolerably by the examination of specimens fractured in different directions ; but the most
satisfactory elucidation of it is obtained from thin sections, especially from such as are
carried in a direction transverse to the longitudinal axis (fig. 38). It is there seen that its
general plan of growth is distinctly " biloculine;" the walls of the principal chambers on the
two sides of tlie longitudinal axis meeting each other along the line a b, just as they do in
Fig. XVI, B (p. 78). But the cavities of these chambers, instead of being hollow, are filled up
with sohd shell-substance, which is perforated by channels whose general direction is
longitudinal, though these are often connected, like the Haversian canals of bone, by channels
passing in a transverse or oblique direction. The longitudinal channels are arranged with,
some approach to regularity ; a row of small orifices being observed to lie just within the
external boundary of each chamber, and thus corresponding with the layer of closely
approximated canals which is brought into view when the surface of the shell is removed by
abrasion (fig. 37, a), whilst a much larger set of orifices, less regularly arranged, nearer to the
internal portion of the chamber, shows that the channels are there much wider, but neither so
numerous nor so closely approximated. The whole system of channels, whose mutual
inosculations bring every part of it into the freest communication with the rest, terminates at
the septal plane in a cribriform aperture (fig. 37, b), resembling that which is normal in
Ilaurrina {^^ l\2), and occasional in yI/27zo/« mxoriim (^110). Another curious feature of
relationship to this last variety of the Milioline type is presented in the very deep pitting by
which the external surface of each chamber is not unfrequently marked (fig. 38, b). This
pitting is afterwards filled up by the calcareous deposit which occupies the cavity of the
chamber formed around it ; so that the innermost layer of this deposit comes to be furnished
with a corresponding set of minute tubercles (fig. 38, a), which may be brought into distinct
view by so fracturing a specimen as to separate this layer from the wall of the penultimate
chamber on which it was moulded, and from which it may be commonly detached without
difficulty. The manner in which these pits and tubercles are mutually appUed to one another
(like the pits on the under side of the epidermis to the papillae of the cutis vera), is seen in
section in fig. 38, a', along the line a b.

1 1 9. Affiniticis. — The genus Fabularia may be considered as presenting the culmination

84 FAMILY MILIOLIDA.

of the proper Milioline type of structure ; that subdivision of the chambers^ which we find to
characterise the liighest types of each series of Foraminifera {% 64), being here superinduced
upon tlie simple MilioUnc type of growth. In the existence of that subdivision we have a
relationship of analogy or parallelism to Orbiculina, Orbitolitcs, and Aheolina ; but in plan
of growth Fabularia is so distinctly related to Miliola, that its genetical derivation is
to be looked for rather in the varietal modifications of the last-named type, than in transi-
tional forms connecting it with those just named, which will be found to have (so to speak)
a distinct line of descent.

120. Geological Distribtdion. — The genus Fabidaria is at present only known in a fossil
state, and it has not been met with elsewhere than in the tertiaries of the Paris basin, being
especially abundant at Grignon.

Genus IX. — Peneroplis (Plate VII).

121. Hisfon/. — The germs Peneroplis was first instituted by Montfort (lxvii) to distinguish
a peculiar type of minute polythalaraous shells, which had been previously described and
figured by Schroter (xcvi) and by Fichtel and Moll (xlv), the latter of whom had ranged it
with numerous others under the comprehensi\'e designation JVauHlus. By Montfort its
distinctive character was correctly indicated as " bouche de toute la longueur de la base, et
percee serialement par une file des pores ;" but he seems to have very erroneously inter-
preted the signification of those pores, imagining that the principal chambers are subdivided
into cells, each occupied by a distinct animal, of which cells the pores are the separate orifices.
Lamarck* (lix), not adopting Montfort's genus, referred the Naufilns planafus oi Fichtel and
Moll to the genus Gristellaria, with which it has no relationship whatever ; but the genus
FeneropJis was recognised by Blainville (vi) and by Ehrenberg (xxxix) ; and D'Orbigny has
applied this name, in his various writings on Foraminifera, to the form described by Fichtel
and Moll, whilst he has created one new generic term, Dendritina, for a series of varietal
forms in which there is a single large arborescent aperture instead of a single or multiple row
of separate pores, and another, Spirolina, for a varietal series in which the spire is prolonged
rectilineally into a row of cylindrical or subcylindrical chambers with an aperture resembling
that of BeridrUbia, this last being the Coscinospira of Ehrenberg.

122. External Characters. — The ordinary form of the shell of Peneroplis (of which an
ideal representation given in Plate VII, fig. 18, is an extremely flat spire, of about two
turns and a half, opening out i-apidly in its last half turn. In the young shell each whorl
usually does little more than adhere to the margin of the preceding, so that the first-formed
portion is but slightly concealed by the subsequent growth ; but sometimes the earliest whorl

* The Renidites of Lamarck and the Remdina of Blainville, which are quoted by Prof.
Williamson (ox, p. 44) as synonyms of Peneroplis, are (as already shown, % 98) aberrant forms of
Verteh-alina.

GENUS PENEROPLIS. , 85

is in great degree overlapped by tlic next ; and it very commonly happens that the last half
whorl spreads itself out to such a degree as entirely to invest the preceding, the extension
even reaching so far as not only to conceal the original umbilicus, but even to encroach upon
the opposite half of the spire (fig. 10). When such is the case, however, the extension
is usually limited to one of the lateral surfaces of the shell, which thus becomes unsym-
metrical. Although this extension is sometimes confined to the inner margin of the spire,
as is seen in fig. 16, yet it often occurs along the outer margin also, being usually limited,
however, to the last four or five chambers. The septal plane extends itself in some
instances around as much as three-fourths of the whole margin of the shell ; thus showing,
even in this type, an obvious tendency towards that cyclical mode of growth which we meet
with in Orbicidina, but which is essentiall}^ characteristic of OrbitolUes. The surface of the
shell is highly polished, and has a peculiarly opaque-white, porccllanous aspect. It is very
strongly marked by depressed bands, which indicate the places of the septa between the
chambers ; and between these septal bands the walls of the chambers rise in flattened arches.
In a direction transverse to the septal bands we almost uniformly observe a strongly marked
striation, the stria; running parallel at tolerably regular intervals, which average about
l-1400th of an inch, from one septal band to another; this striation, which imparts a very
characteristic physiognomy to these minute shells, seems due to a sort of plication or ridge
and furrow arrangement of the slielly wall (Plate VII, fig. 20), which may not improbably
have the effect of imparting to it increased strength. The plication generally disappears at
the junction of the walls of the chambers with the septa, and consequently we do not usually
see it at the septal plane when the shell is viewed endways. Sometimes, however, it is con-
tinued on to the septal plane itself; and its character is then extremely well displayed, as in
fig. 15, which, however, represents not the typical form, but one of the varieties to be
hereafter noticed. On the prominences of the plicse, there are frequently to be seen rows of
extremely minute punctations (fig. 20) ; these, however, are not the apertures of passages
through the shell, as might not unnaturally be supposed, but are mere depressions of its surface,
as I have ascertained by the careful examination of veiy thin sections. It is remarkable that
the plication of the shell is sometimes wanting, though the punctations may still present
themselves in rows, as shown in fig. 2 ; whilst, in other cases, not only are the plicEC deficient,
but the punctations are distributed uniformly over the entire surface, as shown in fig. 3.
That these variations are not indicative of any specific difference, is at once proved by the
fact that the shells which exhibit them in one part present the ordinary character of surface
in another. Similar punctations occasionally present themselves on the septal plane of
aberrant forms of the PenerojAls type.

123. The septal plane is perforated by numerous isolated pores, which, in those
extremely compressed specimens that constitute the most typical examples of this generic
form, are arranged in a single linear series (figs. 16, «, 18) ; the number of these pores
depends upon the length of the septal plane, and thus it usually increases with the age
of the individual, each chamber opening externally by a larger number of pores than did that
which preceded it. The typical form of these pores seems to be circular, though they are
apt to present various departures from that shape ; they usually lie in a sort of furrow

36

FAMILY MILIOLIDA.

formed by the projection of the lateral borders of the mouth somewhat beyond the septum,
and each one is suiTOunded by a prominent annulus of shell.

124. Internal Structure. — On examining a thin section of a typical Peneroplis, taken
through the median plane between the lateral surfaces (Fig. XIX), the central chamber is

Fig. XIX.

Section of Peneroplis through the median plane.

seen to have the globose form which characterises the primordial segment of the Fora-
minifera generally ; from this first chamber a sinfjie passar/e leads to the second, which com-
municates in like manner by a single passage with the third, as does the third with the
fourth; the fourth chamber, however, communicates by ^2i?o/iassayes with the fifth, as does
the fifth with the sixth, and the sixth with the seventh. In the septum between the seventh
and the eighth, with which the second whorl may be considered as commencing, there are
three apertures ; and this number continues for the four consecutive partitions which divide the
chambers forming the next half-convolution. Then, however, commences a very remarkable
increase; for whilst in each of the next two partitions there nve/our passages, the numbers
in the four succeeding partitions which divide the chambers completing the second turn are
i-espectively 6, 9, 11, and 14; whilst in the last eight partitions which divide the chambers
of the outer half- whorl, the numbers of the apertures are respectively 14, 20, 2G, 38, 30, 3.5,
44, and 48. The average distance of the apertures from each other remains nearly the same
throughout; so that their number pretty closely corresponds with, and may be taken to
represent, the length of tlic septal plane which they traverse in each case ; and it is not a
little remarkable, that whilst this number should only increase from 1 to 4 in the first
convolution and a half, it should so, rapidly augment from 4 to 48 in the last half-convolution.

12.5. As I have not been fortunate enough to obtain any other than dried specimens of
this organism, I have not had the opportunity of examining the structure and arrangement
of its soft parts. It is obvious, however, that the body of the animal will consist of a series of
compressed, flattened segments, progressively increasing in their transverse diameter, and
communicating with each other by multiple threads or " stolons" of sai'code, the number of

GENUS PENEIIOPLIS. 87

which will augment with the length of the septal plane, whilst through the multiple pores of the
last septal plane the sarcode-body can extend itself into pscudopodia. These may coalesce
at their bases to form a continuous segment, on which a ne\A' chamber will be moulded when
the growth of the body requires such an extension of the shell*

126. Variefk's. — The most frequent departure from the typical form presented by
Fenewjjlis is that represented in fig. 12 ; in which we see that, instead of opening out and
encroaching on the previous whorls, the spire becomes disengaged, and prolongs itself in a
straight hne, its successive chambers exhibiting little or no increase in size. Between this
and the typical form every intermediate gradation presents itself; and it is curious that
even here a transverse extension sometimes takes place, quite suddenly, by a doubling
backwards of the last three or four chambers along the inner margin of the straight portion.
In these elongated varieties of Fencroplis we find the spire less compressed, so that the septal
plane is wider in proportion to its length (fig. 12, a); and this condition, which is also
frequently encountered in specimens that have not thus extended themselves, is almost
always coincident with a duplication in the series of pores in the septal plane. Now, it is not
a little remarkable that this is almost uniformly the case with specimens furnished by
particular localities, whilst those obtained from others not very remote exhibit almost as
uniformly the extremest elongation and narrowing of the septal plane, with only a smgle
row of apertures ; and hence it might not unreasonably be maintained that this difference
should be accounted of specific value. In reply to this, however, there is not only the
analogy of Orbiculina and OrbitoUtes, in which (as we shall hereafter see) an indefinite
multiplication in the rows of inarginal pores may take place during the growth of tlie
individual, but also the fact that in Penerojjlis the two forms cannot be distinguished at an
early age, either by the shape of the shell or by the disposition of the pores, which are often
arranged neither in a single nor in a double row, but on a sort of mixture of both plans, as
shown in figs. 6, a, 10 ; whilst among the more advanced examples of each type it is not at all

* A figure is given by Prof. Elirenberg (xxxis, taf. ii, fig. 1), professing to represent the
decalcified body oi a. PeneropUs obtained alive from the Red Sea, which corresponds with the description
above given in every important particular save this, that the successive segments are connected along
the inner margin of the convolutions by a baud much broader and thicker than the threads which
pass between other parts of the segments ; so that this baud would seem to establish a principal con-
nexion, to which the other threads might be considered as secondary. Now after a very careful
examination both of the septal planes of numerous specimens and of sections taken in the direction of
Fig. XIX, I feel myself justiQed in tlie positive assertion that no such principal aperture exists at the
inner margin of the septum, as would be required to give passage to such a band as is figured by
Prof. Ehrenberg. Consequently I can only account for this feature in his delineation of the animal
(the idea of a difference in the conformation of the shell being negatived by the precise correspondence
between his figures of it and my own, as well as by my familiarity with the Red Sea type of
PeneropUs), by supposing that, like some of his other figures, it rather represents his idea of the
structure of the animal than what he actually saw iu its body, this principal baud being apparently
regarded by him as an intestinal canal by which he supposed all the segments to be connected
together.

88 FAMILY MILIOLTDA.

uncommon to meet with individuals which present i\ combination of the characters of both,
the septal plane having a single row of pores in one part of its length with a double row in
another (sec ex, fig. 85). Sometimes, moreover, in one of the less compressed forms of the
shell, although there is but a single row of pores, it is obvious from their elongated shape
that there is an incipient tendency to duphcation (fig. 8). Hence I consider that it may be
unhesitatingly asserted that the duplication of the row of pores, and the increased turgidity of
the spire which it accompanies, are but features of individual variation, and cannot be
admitted to rank as specific differences ; and in this view I am glad to find myself borne out
by Prof. Williamson, who (ex, p. 44) defines Peneroplis, not (like M. D'Orbigny) as
having only a single row of apertures, but as having " septal orifices scattered over the long,
narrow, septal plane."

127. A much wider departure from tlie typical PcncfopJls, however, is presented by that
group of forms which D'Orbigny has separated under the generic designation iJraiJ^nYzwa;
and according to the usually received notions on the classification of Foraminifera, such a
separation would seem fully justifiable. These forms are especially characterised by the
possession of a single large apei'ture, sending out dendritic ramifications, in each septum
(Plate VII, figs. 1, 14) ; but this is by no means the whole of their differentiation. For the
spire, instead of being compressed, is very turgid (fig. 13); and its successive whorls not
merely surround those which have preceded them, but also invest them with broad alar pro-
longations {al, fig. 14, h, (■), those of the chambers of even the last whorl often extending
neai'ly to the umbilicus. The geographical distribution of Dnidritina, moreover, is peculiar ;
for, so far as I am aware, this type is restricted to tlie tropical ocean. I have not met with
it in dredgings from any part of the Mediterranean or the Red Sea, where Peneroplis
abounds ; while the largest specimens I have seen are those furnished by Mr. Cuming's
Philippine explorations, some of which measure '078 inch in diameter, and '030 between the
lateral surfaces. To such as content themselves with glancing at strongly marked examples
of this type, the propriety of its generic, or at any rate of its sub-generic, separation from
Peneroplis would seem indubitable. Nevertheless I think that I shall be able to show
adequate grounds for the belief that the two forms cannot be separated by any definite line of
demarcation, and that they must therefore be ranked as not merely belonging to the same
genus, but even as varieties of the same species.

128. In the first place, I would refer to the fact that the peculiar plication and puncta-
tion of the surface of the shell, which are such marked features in the physiognomy of
Peneroplis, are repeated in Dendritina (fig. 21) in a manner so precisely similar, as strongly
to impress every one who has his attention directed to the aspects of these two forms
respectively with the idea of their very close relationship. Secondly, we observe in
Dendritina precisely the same tendency to rectilineal extension in the later period of growth
as in Peneroplis; for although the distinct generic term Spirolina has been given to the
form presenting this modification, it is obvious that the example delineated in fig. 4
bears just the same relation to the typical Dendritina, that the one shown in fig. 12 bears
to the typical Peneroplis. The transition from Dendritina to SjnroHna is well seen in fig. 13,
in which we see that the last whorl is just about to disengage itself from the earlier ones.

GENUS PENEROPLIS.

89

and that its continued increase upon the plan which has ah-eady begun to manifest itself
would convert it into a Spirolina. On the other hand, the Spirolina represented in fig. 4
has, up to the time of the substitution of the rectilineal for the spiral mode of growth, all the
characters of an ordinary BendnHna.* Thirdly, the differences of general configuration
between Peneroplis and JDendritina are differences of degree, and present themselves in
very variable amount in different individuals. For, starting from those forms of Peneroplis
in which the spire is least compressed, the transition is easy to those Bendritince whose spire
is least turgid, and whose septal plane is not broader in proportion to its length than it often
is in Peneroplis. From the most compressed forms of Bendritina to those which have the
most turgid spires and the widest septal planes the gradation is insensible, scarcely any two
individuals according in their proportions; thus we find that whilst the septal plane is
sagittate in some (Fig. XX, A, c), it tends to become reniform in others (b, d), the margin of

P'IG. XX.

B c

Front views of four specimens of Dendritina.

the spire, which is almost carinated in the first case, becoming obtuse and even crescentic in
the second. Again, the extent of the investment of the earlier whorls by the latter varies as
much as the degree of turgidity; forwhilst in some of the most compressed forms, as in Peneroplis,
each whorl does little more than apply itself to the margin of the preceding (Fig. XXI, a, c),
the more turgid the spire becomes the more completely (generally speaking) does it embrace
the preceding, the alar prolongations of the chambers thus coming to bear a large proportion
to their principal cavity (Fig. XXI, B, d).

129. Still it may be said that, notwithstanding all these points of resemblance, the
difference between Peneroplis and Bendritina is clearly marked out by the difference in the

* The elegant crozier-like form of Spirolina is sometimes rudely imitated by Lituola , aud

specimens of the latter, the Sp. agglutinans of D'Orbigny (lxxiii, p. 137) for example, have not unfre-

quently been described under the former designation, although the texture of the shell, which is never

arenaceous in Spirolina, and always arenaceous in Lituola, aftbrds a ready aud certain means of

discriminating them.

12

90

FAMILY MILIOLIDA

modes of communication between the chambers of the two types, and that such a difference is
sufficiently important to constitute a vahd generic character. I freely admit that this would
be the case, if the difference were constantly to present itself between all the individuals of the
same type, as it does between their characteristic examples (Plate VII, figs. 13, 16); but the
fact is far otherwise. We have seen that among those which would be unhesitatingly ranked
under the designation Feneroplis, there is not only a tendency to multiplication of the rows of
separate pores, but also an occasional fusion of two or more pores, so as to form a single large
pore of irregular shape. On the other hand, among the unquestioned DeiidritincB we observe
not merely that the form of the single large dendritic aperture is extremely variable, but that
it is frequently so simple as to suggest the idea of having been formed by the coalescence of a
linear series of pores. The highest development of the dendritic form of aperture that I have
met with, is shown in fig. 14, a, b ; two examples of a remarkable departure from this have
just been seen in Fig. XX, b, d, where the proportions of the aperture are altogether
reversed, its breadth being much greater than its length, and its central part being enlarged
at the expense of its ramifications ; while, on the other hand, in Fig. XX, a, c, we have
marked examples of a narrowing and elongation of the aperture, with such a reduction of its
dendritic ramifications that it comes to present little more than a linear fissure. From a
comparison of these cases it will be seen that the form of the aperture bears a pretty constant
relation to that of the septal plane ; the broadest apertures presenting themselves in the
individuals which have the most turgid spire, and the narrowest in those whose spire is most
compressed ; whilst the proportionate development of the two principal alar prolongations
seems related to the degree of that alar extension of the chambers over the whorl they enclose,
of which I have already spoken. But the most satisfactory proof of the wide extent of range
of variation in the form of the aperture in Dendritina, is afforded by a comparative examination
of the apertures connecting different chambers of the same individual. Thus, in the interior
of the very shell (fig. 13) that presented the peculiarly characteristic example represented in
fig. 14, we find a form of aperture closely corresponding to that shown in Fig. XX, c ; and
in four septa of the inner part of another shell we have the simple forms of aperture repre-
sented in Fig. XXI, a, b, c, d.

Fig. XXI.

A. ■ ^ B

Septal planes and apertures from different parts of the same specimen of Dendntitw.

l30. But further, not only do we thus meet with examples of each type which present
more or less of approximation towards the other, but we also not unfrequently encounter

GENUS PENEROPLIS. 91

individuals in which the characters of the two types are so blended as to make it difficult, if
not impossible, to say to which they should be referred. Thus in the specimen (fig. 10)
already referred to as presenting a linear series of pores, the marked elongation of which
shows each to be formed by the coalescence or imperfect separation of two, there is an addi-
tional pair precisely in the situation of the alar prolongations in fig. 14, c ; and it is obvious
that the simple form of dendritic aperture there represented would result from the coalescence
of these pores. along the middle of the septal plane. Another example, also from a young
specimen, is shown in fig. 6 ; and it is readily intelligible how in such a case the subsequent
compression of the spire and the narrowing of the septal plane may cause the pores to
present the simple linear arrangement characteristic of PencropUs ; whilst if, with a
continuance of the early mode of growth, the separate pores of later septa should coalesce
into one aperture, we should have a Bendritina. In another young specimen, shown in
fig. 11, such a fusion of several pores into a single dendritic aperture has actually taken
place («), whilst another broad aperture is seen just below this. Again, in fig. 7 we see the
broad septal plane irregularly perforated by numerous pores, some small and rounded, others
large and irregular, each of the latter being obviously formed by the coalescence or imperfect
separation of two or three ; the turgid spire of Bendritina and the separate pores of Pene-
roplis here coexisting with each other, so as to make it difficult to say to which type the
specimen should be referred. Again, the transition is easy from the specimen represented
in fig. 10 to that shown in fig. 9, and thence to the one whose septal plane is shown in
fig. 15 ; here the coalescence has proceeded so far as to produce a number of separate
branching apertures, and nothing is wanting but the removal of the line of shell which
passes down the middle of the septal plane to unite these into the mo§t characteristic form of
the single ramifying orifice. This individual, like the one represented in fig 13, was already
beginning to assume the Spirolinr form, the rounded shape of the mouth showing that the
spire has detached itself completely from the previously formed convolutions ; in figs. 4, «,
and 5 are shown the septal planes of more advanced examples of the same type, which
present such a combination of the large dendritic apeilure of Bendritina with the isolated
pores of Peneroplis as to complete (in my opinion) the proof that no valid distinction can be
drawn between these two types, either from the number, the isolation, the position, or the
shape of the apertures in the septa. Hence it follows that not merely must the genera
Bendritina and Spirolina be relinquished, but that both these forms must be regarded as mere
varieties of Peneroplis platiafus.

131. Affinities. — A sort of sketching out of Peneroplis may be traced, as we have seen,
in some forms of Nubectdaria (% 90) ; and the type becomes still more defined in Ferte-
hralina, some of whose forms can only be distinguished from Peneroplis by their undivided
aperture. If the elongated sht of the compressed Vertehralince were to be subdivided into
a linear series of pores as in the typical Peneroplis, or the circular aperture of the cylindri-
form variety were to be modified in like manner so as to resemble that of Spirolina, the tran-
sition would be complete. Again, we have seen that an approximation to the Peneropliform
type is presented in the cribriform subdivision of the aperture of a true Miliohi (f 110),
whilst a still closer relationship to it is exhibited in the Hanerine modification of the Milioline
t)rpe (^ 112). Looking to the inconstancy of the aperture in the Peneroplis type itself, we

92 FAMILY MILIOLIDA

can scarcely fail to perceive how slight are the differential characters which separate it from
either Vertehralina or Hauerina. On the other hand, it presents a very close approximation
to the spiral variety of Orbiculina ; a sort of preparation for the subdivision of the chambers
characteristic of that type being made in the subdivision of the aperture, and perhaps also
in the ridge-and-furrow arrangement of the lateral walls of the chambers. And, as we shall
hereafter see {% 143), there are certain aberrant forms of Orbiculina in which the subdivision
of the chambers is wanting, so that no perfectly defined boundary between these two types
can be said to exist.

132. Geographical Distribution. — The genus Peneroplis is very widely diffused through
warmer latitudes, especially frequenting the laminarian zone ; so that few collections of Fora-
minifera from sands or dredgings brought from the Mediterranean, the ^gean Archi-
pelago, the Red Sea, the East or West Indies, the Philippine Seas, or the shores of Australia
or the Polynesian Islands, will fail to present numerous examples of it. A few specimens
have been found on British coasts ; but it seems most probable that, as Prof. Williamson has
suggested (ex, p. 46), these have been brought by the Gulf Stream from the West Indian
Seas. The prevalence of particular modifications seems in some degree determined by
temperature. For it is only in tropical seas that the Dendritine variety presents itself
127); and although the ordinary type also abounds in the same localities, yet it is there
that it shows the greatest tendency towards the dendritine variety, both in the turgidity of
its spire and in the arrangement of its septal pores, whilst the Spiroline variety generally
shows some tendency to the dendritic form of aperture. In the Red Sea the ordinary
Peneroplis is very abundant ; and in its young state the spire is turgid, and its pores are
frequently arranged in a double row or even tend to coalesce, though with each addition to
the number of segments the spire becomes flatter and broader, and in the older specimens
the pores are almost invariably arranged in a single row. Now here the proper Dendritine
variety is either absent altogether, or is extremely rare ; and the Spiroline (which presents
every gradation from the cylindrical to the compressed form) rarely has any other kind of
aperture than a multiplication of separate pores. In the Mediterranean, on the other hand,
which seems to be the most northern limit of its diffusion, not only is the Bendritine variety
altogether wanting, but the Peneroplis type seems (as it were) to be starved out, the spire
presenting the extreme of attenuation, and the septal pores being almost uniformly arranged
from the beginning in a single row. — The Spiroline variety, which is usually of smaller
dimensions, seems to replace both the Dendritine and the Peneroplis type in the deeper waters
of the tropical ocean ; both the large turgid Bendritina and the broad Peneroplides being
inhabitants of comparatively shallow water.

133. Geoloyieal Bistribution. — Neither the ordinary Peneroplis nor its Dendritine and
Spirolme varieties has been traced backwards in geological time further than the commence-
ment of the Tertiary epoch.* The Grignon and Paris Tertiaries contain several forms of

* The statement of some authors that Spirolina occurs in the Cretaceous and even in earlier
formations of the Secondary epoch, has resulted from their having mistaken the crozier-shaped forms
of Lituola for the true Spirolina.

GENUS ORBICULINA. 93

Peneroplis and Spirolina, to the exclusion of Bendritina ; whilst in the Vienna Tcrtiaries we
meet with Dendritinn and Spirolina, to the exclusion of Peneroplis.

GenusX. — Orbiculina (Plate VIII, figs. 1 — 12)

134. History. — The interesting group of organisms belonging to this type seems to

have early attracted notice, probably on account of the great abundance in which it presents

itself on the sands of many of the West Indian shores. Three species are described

and figured by Fichtel and Moll (xlv), under the ^ames oi Nautilus orbictdus, N.anr/ulatus,

and N. aduncm. Lamarck (lix), however, separated them from Nautilus, and raised them

to the rank of an independent genus, to whicii he gave the name of Orbiculina ; and he also

changed two of the specific names, the three standing respectively as 0. numismalis,

0. angulata, and 0. uncinata. By Montfort (lxvii), these species were raised to the rank

of independent genera, under the names of Helenis, Archaias, and Hates ; but these genera

have not been adopted by any other systematist. M. d'Orbigny, in his first classification of

the Foraminifera (lxix), not merely adopted Lamarck's generic designation, but afiirmed

that the three reputed species were really nothing else than one and the same organism in

difi"erent phases of growth, 0. angulata being the youngest, 0. numismalis the next in age, and

0. 7incinata the adult. He arrived at this result, of the truth of which I am myself well

assured, by the comparison of a great number of specimens, a process which it would have

been well for science if he had more constantly adopted. The name of the adult form

should, of course, stand as that of the species; but the organism in question is more commonly

known under the designation Orbiculina adunca, which seems to have been conferred upon it

by M. Deslongchamps (xxxii). A considerable number of figures of this species are given

by M. d'Orbigny in his treatise on the Foraminifera of Cuba (xcii) ; they serve only,

however, to give a general idea of the diversities of external conformation which had

presented themselves to him ; and notwithstanding their number and variety, they do not

include some of the most important among the protean shapes of these bodies, nor do they

throw any light upon their internal structure- The memoir of Prof. Ehrenberg, in which

his group of Bryozoa was originally constituted (xxxix), contains the first recognition of the

near relationship between Orbiculina and Orbifolites, which he grouped in close proximity

among the Bryozoa. His description of their structure, however, is so greatly prejudiced

by his erroneous idea of the nature of the animal body to which they belonged, and is

rendered so imperfect by his want of acquaintance with the appearances presented by their

sections, that it serves rather to mislead than to infoi'm any one who may consult it. It was

by Prof. Williamson (cviii) that the real structure of OrhicuUiia, and its very close conformity

to that of Orbitolites as previously described by myself (xii), were demonstrated ; and that

the frequent exchange of the spiral for the cyclical plan of growth, witli the advance of age,

was recognised ; and the few slight errors into which he fell are probably attributable to the

imperfect state of the specimens on which his description was founded.

94 FAMILY MILIOLIDA.

135. External Characters. — The form under which Orhiculina is most commonly known
is that represented in Plate VIII, figs. 8, 9, 10, which has suggested the specific designation
admica; but such a departure from this as is shown in figs. 1, 2, 3, 4, is not at all infrequent;
and a continuance of the mode of growth which characterises these last sometimes leads to
the assumption of the discoidal form shown in figs. 5, 6, which seems to be the highest phase
of this type, being always presented by the largest specimens of it, some of which attain a
diameter of '20 of an inch. Among young specimens it is not at all uncommon to meet with
some (fig. 2) that bear a strong resemblance in form to Peneroplis ; they are distinguished
from that type, however, by the absence of the striation that so generally characterises it ;
and when the surface-layer of shell is sufiiciently thin, a division of each principal chamber
by secondary partitions passing between the septa at right angles to them may also be very
commonly made out. In older specimens, however, these secondary partitions are seldom to
be seen externally, being usually obscured by the greater thickness of the surface-layer of
shell ; sometimes, however, they continue to be distinguishable even in the most developed
forms (fig. 5). The large discoidal specimens bear so strong a resemblance to Orbitolites as
not to be distinguishable from that type except by the prominence of the umbilical region,
which is occasioned by the investment given by each turn of the spire to the preceding, so
long as the spiral growth continues.

136. The essential unity which prevails through these and other less important diversi-
ties will be understood by following the growth of Orhiculina from that early condition
shown in fig. 7, which is common to all. Its form is then lenticular, or even, in the thicker
varieties, almost orbicular ; each septal band, commencing from the centre (a) of the spire,
goes off, in the first instance, in such a manner as to encroach on the opposite side of the con-
volution; it then curves round with a strong convexity directed forwards {h), turns back,
and finally terminates at the margin (r) in such a manner as to form its continuation. By
this curvature the septal plane («, h, c), which, as yet, corresponds to only half the diameter of
the spire, is greatly elongated, so as to present a much larger apertural surface than it would
possess if it passed directly from the centre to the margin in the line a r. When viewed on its
anterior face, it has the form of that of a PeiieropJis whose spire completely invests the
preceding; its breadth varying in proportion to its length, as the shell is orbicular or lenticular
in shape, but its alar lobes being always much prolonged. Its entire surface is perforated with
pores exactly resembling those of Peneroplis, each being surrounded by a prominent annulus
of shell ; and these pores show some definitcness of arrangement, being disposed in
more or less regular rows, as to the number of which, however, there is no constancy
whatever. In a more advanced stage of growth (fig. 8), we see that the septal band,
still commencing at the centre («), and partly encroaching on the opposite side of the
spire, then bends round as before ; but instead of speedily turning backwards, it makes
a gentle curve [h], which forms a large part of the margin of the shell, and then
terminates abruptly at c, this termination being the source of the " aduncal" form.
Here we see that the septal plane with its apertural surface is greatly extended ; and along
all that portion of it which forms the margin of the shell, the pores are disposed with more
approach to regularity, the number of rows, however, being very variable. In a yet more
advanced stage of the " aduncal type," the later portion of the spire ceases to invest the

GENUS ORBICULINA. 95

earlier, the newest chambers stopping short at its margin or but slightly encroaching on it
(fig. 9, a) ; and the septal plane, which now forms from, two-thirds to three-fourths of the
entire circuit, is much narrower in proportion to its augmented length, more resembling that
of an advanced Fencrojj/ia {VMc VII, fig. IG, f/), but usually showing multiple rows of pores.
This mode of increase may continue during the whole life of any individual, so that speci-
mens attaining a diameter of -12 of an inch not unfrequently preserve the " aduncal" shape.
But it often happens that the outer extremity of the newly formed chambers (fig. 4, <••), instead
of abruptly terminating at the most anterior part of the margin, extends itself by an inward
curvature, so as to double back upon the earlier portion of the spire, and thus to approximate
the inner extremity of the same chamber (fig. 4, «) ; and the septal plane with its apertural
surface is thus carried round nearly the entire circuit of the shell. A persistence in the
same plan of growth causes the two extremities of the chambers to meet and completely
. to surround the original spiral (fig. 5) ; and from that time forth each new chamber forms a
complete and continuous ring around the preceding, and the apertural surface of the septal
plane extends round the entire circuit. In the most advanced stage of its growth, the disk
often thins out to such a degree that the apertural margin is no broader than that of a
Feneroji/is, and has, like it, only a single row of pores.

137. Now this change from the s/jiral to the cyclical plan of growth may take place at
any period of life. In the individuals represented in figs. 1 and 3 there is obviously a
preparation for it ; these showing no tendency to that abrupt termination of the outer ends of
the later chambers which gives rise to the " aduncal" form, but, on the other hand, exhibiting
a marked disposition to the extension of these towards their inner extremities, so that they
will assume the discoidal form without passing through what is usually the intermediate
stage. Hence it is impossible to regard it in any other light than as a varietal modification,
the conditions of which are as yet unknown, though related in some degree to the advance
of age.

138. The shell of Orhmdina corresponds closel)^ in texture with that of Peneroplis,
having (in well-preserved specimens) very much of the same polish and enamel-like lustre.
Its surface is frequently marked (like that of the Miliola) by pits which present the semblance
of pores, and which have been mistaken for them by Prof. Williamson (cviii). A careful
examination of thin sections, however, makes it clear that the continuity of the shelly wall is
nowhere interrupted.

139. Internal Slructurc. — In a large proportion of ordinary specimens of Orhicidina
the natural surface has been so far removed by abrasion as in some degree to disclose the
internal structure of the shell ; this, however, is much better displayed by thin sections
carried through the median plane, such as those represented in figs. 6, 10, 11, and by sections
taken at right angles to this, such as that represented in fig. 12. An idea of the structure
will be best formed by supposing each elongated galler}'' which forms the chamber of a
Penerojjlis to be partially subdivided into " chamberlets" (if the coinage of such a diminu-
tive be admissible) by a series of partitions that pass transversely from each septum to the

96 FAMILY MILIOLIDA.

next ; all the " chamberlets" of the same row, however, communicating with each other by
a passage that runs continuously through their partitions (see Diagram, p. 52) ; and each
" chamherlet " also communicating with the chamberlets of the adjacent rows by perforations
in the principal septa. This is, in fact, exactly what we see in the peripheral portion of
those thinned-out specimens of discoidal Orbicidince which have but a single row of marginal
pores, as will be clearly understood from fig. 1 1 , which represents a part taken from the
edge of fig. 6, seen as an opaque object under a much higher magnifying power. At
na', ad , ad, ad are seen portions of four of the principal septa which separate from each other
the principal chambers or galleries cc', cc', re' ; these galleries are again divided into the
" chamberlets " d, d, d by the secondary partitions e, e, e, e, which do not, however, com-
pletely separate them from each other ; and the successive galleries communicate with each
other by the passages I/, b, that traverse the principal septa, those of the last-formed septum
showing themselves as a row of pores upon its external surface. The animal body which
occupies the interior of a shell thus divided will obviously consist (as we shall see to be the
case in Orlitolites (Plate IV, figs. 14, 23) of a series of principal segments of sarcode, each
of which is divided by constrictions into a necklace-like series of sub-segments, strung
(as it were) upon a connecting cord ; whilst each principal segment will communicate with
the segments anterior and posterior to it, as in Peneroplis, by stolons of sarcode that pass
through the septal passages, those of the last segment issuing forth as pseudopodia from the
marginal pores.

140. It is seldom, however, that the arrangement is so simple as in the case just cited;
for it much more frequently happens that the space between the two surfaces of the shell
exceeds by many times the distance between each septum and that which succeeds it, so that
the " chamberlets '' are greatly elongated in the direction perpendicular to the surface. This
is shown in fig. 12, which represents the central portion of a section whose plane passes
at right angles to that of the spire, and brings into view the successive convolutions 1, 2 2',
•3 3' and 4 4', of which each is seen completely to enclose the preceding. Each " chamherlet "
is here elongated vertically, and the adjacent " chamberlets " of the same series communicate
with one another, not by one passage, but by many (a) ; whilst the successive series also
communicate with each other by multiple rows of septal pores {b). In neither set of communica-
tions, however, do we observe any great regularity, whether as regards number or arrange-
ment. The height of the chambers, with the number of the connecting passages proceeding
from them in each direction, is seen to increase progressively from the first-formed convolu-
tion (1), whose chambers are disposed upon the simple type previously described, through
the second (2 2') and third (3 3') to the fourth (4 4'), in which last it reaches its maximum at
no great distance from the centre ; and from this it often diminishes as the chambers
extend themselves more and more widely along the margin, which (as already stated) may thin

out until we find in the peripheral portion a recurrence to the simple type of the central

The disposition of the sarcode-body that occupies this more complex system of chambers
must obviously be modified in correspondence with it, as we shall see in the complex form of
OrbitdUfcs (Plate IV, fig. 25). The subdivisions of each principal segment, instead of resembling
beads strung upon a single cord, will rather have the form of a row of columns standing side
by side, and connected together by numerous bands passing transversely from one to the

GENUS ORBICULINA. 97

other ; whilst similar multiple bands pass from each series to the rows that stand behind and
in front of it,

141. A comparison of figs. 6 and 10, — of which the former represents the internal
arrangement of the cyclical type, and the latter that of the aduncal, — shows that the early-
growth of the former, up to the period when the mouth of the spire widens out on both sides,
takes place after precisely the same fashion as that of the latter ; after which the aduncal
termination is concealed by the extensions of the subsequently formed chambers along its
margin, which extensions, having once advanced far enough to meet those advancing in
the opposite direction, unite with them, so that each gallery of " chamberlets " thenceforth
returns into itself, instead of terminating by two blind extremities. A conception of the
probable mode in which the successive additions are made to the shell will help us to under-
stand how the one mode of growth may be exchanged for the other, without any departure
from the fundamental plan. The extensions of the sarcode-body which form the pseudo-
podia issuing from the marginal pores will first coalesce with each other at their bases, so as
to form a continuous segment which will lie along the external surface of the last septum ;
if this segment were of uniform size along its whole length, the shelly chamber formed by
the calcification of its surface-layer would be simple, like that of Peneroplis ; but it is thick-
ened in front of each septal pore, and narrowed in the intervals between these thickenings,
so as to form a series of secondary segments united by a continuous stolon ; and the shelly
envelope moulded upon this will have a corresponding series of " chamberlets " connected by
a continuous gallery. Now the tendency of each new segment of the sarcode-body is usually to
extend itself along the margin beyond the preceding; but this extension is commonly limited
in the early growth of Orhkulina to the inner extremities of the successive segments, which
gradually creep round the earlier portion of the spire, whilst their outer extremities terminate
abruptly, and may continue so to do through the whole of life. But if these outer extremities
of the segments of sarcode should share in the extension, they will creep along the margin
of the older part of the shell in the contrary direction, until they meet and coalesce with
those of the inner extremities ; and from that time each successive segment of sarcode will
be a complete ring which will encircle the entire margin of the disk, and the successive
additions made to the shell will be formed upon the cyclical plan.

142. A larger size and higher development are attained by some fossil forms of
OrbicuHna, which there is nevertheless no sufficient ground for regarding as specifically
different from the existing type. Under the erroneous designation of Orbitolites Malabarica,
Mr. Carter has described (xx) a species of OrbicuUna that abounds in a Tertiary hmestone
apparently corresponding with the Nummulitic limestone of the South of Europe ; and of
this species I have, through his kindness, had the opportunity of carefully examining several
examples. In size it greatly exceeds the existing type, its diameter being sometimes as much
as seven or even eight lines ; in general structure, however, it altogether conforms to the
description already given, with this one exception, that each surface is formed (as in the
complex type of Orbifolitcv) by a layer of shallow chambers that are partially cut ofi" from
those of the thick intermediate substance. This difference, however, possesses no greater
claim to be accounted a specific distinction in OrbicuHna than it does in OrbiloUtes ; and since,

13

98 FAMILY MILIOLIDA.

when we come to examine into its value in the latter type, we shall there find it to be a mere
varietal or developmental diversity, it cannot here be accepted as of higher value.

143. Affinities. — The genus we have been considering occupies a position precisely
intermediate between PeneropKs and Orbitolifes, to both which types it is most intimately
related. As already mentioned, young specimens of Orhiadina are often to be met with
which bear a very strong external resemblance to Pcnerojilis ; and even the absence in the
former of the striation usually characteristic of the latter does not furnish an absolute ground
of differentiation, since the striation is not unfrequently obsolete in Peneroplis (f 122). In
ordinary cases, however, the difference becomes evident so soon as we examine into the inter-
nal structure of Orliculina ; being marked by the subdivision of the principal chambers into
" chamberlets " by the partitions which extend transversely between the septa. It is a fact
of not a little significance, however, that those partitions are sometimes wanting, not merely
in feebly developed peneropliform varieties, but even in good-sized adunciform specimens ;
so that the chambers are formed upon the model of those of Peneroplis, and must be occu-
pied, as in that genus, by transversely elongated lobes of sarcode, instead of by a monUiform
series of sub-segments. In such cases, therefore, no absolute line of demarcation can be laid
down between Peneroplis and Orbicidina ; for, although there may be practically little or no
difliculty in referring any given specimen to one or the other type, by the aggregate of the
characters it presents, yet no one of these characters taken by itself is sufficiently constant
to serve as the basis for a precise definition. So, on the other side, the resemblance between
the peripheral portion of an OrbicuKna that has taken on the cyclical growth, and the
corresponding portion of those varieties of Orbitolites in which the superficial chambers are
not differentiated from those of the intermediate stratum (^ 173), is so extremely close, as
well in internal structure as in external aspect, that the two could not be distinguished by
anv character or combination of characters. It is, in fact, only in their early mode of growth
that Orbicidina axidi Orbitolites essentially differ from each other; the former being always
spiral, whilst the latter is ti/jjicalli/ cjcYicdX from its commencement. But we shall see (^ 180)
that the early growth of Orbitolites is often spiral ; and the difference between the two types
seems to resolve itself essentially into this, that the spiral mods of growth gives place to the
cyclical in Orbitolites before a second convolution is formed, so that the primordial chamber
and the first convolution are never invested by subsequent growths.

144. Geo(/rapJtical Distribution. — This generic t3^pe appears to be limited to the warmer
parts of the ocean. It is found in great abundance near the shores of the West Indian
Islands, also near those of the islands of the East Indian and Polynesian Seas, being especially
large and abundant in the neighbourhood of the Philippine Islands. It occurs also in the Red
Sea, and is asserted to present itself in some parts of the Mediterranean and in the ^gean,
though it is certainly not a common inhabitant of those seas. So far as is at present
known, Orbicidina is entirely deficient in the seas of colder latitudes.

145. Geological Distribution. — We have at present no certain knowledge of the existence
of Orbicidina in any formation anterior to the Tertiary series ; but in several members of this
it is very abundant. A fossil form closely resembling that of the Malabar Limestone has been

GENUS ALVEOLINA. 99

found in the Tertiarics of St. Domingo ; and the type is also found fossil in a white
(Tertiary ?) limestone at Corfu.

Gejius IX.— Alveolina (Plate VIII, figs. 13—15).

146. Histori/. — Most of the examples of this type at present known are fossils, occurring
in association with Nuutiutilites, Orhltolites, &c. in the Nummulitic limestone, or in other
formations which represent it ; and those first described (by Fortis) were confounded with
Nummulites and Orbitolites under the term Discolithus. By Fichtel and Moll (xlv) they were
ranked as a sub- type of their comprehensive genus Nautilus. The designation Alveolites was
first given to this type by Bosc,* who erroneously referred two minute forms of it to a genus
which had been previously established by Lamarck (lvii) for a group of corals ; but Montfort,
(lxvii), not accepting this determination, raised three of Bosc's species to the rank of genera,
under the names of Borelis, Clausulus, and Miliolites. Lamarck did not adopt either Bosc's
or Montfort's generic designations, but substituted new ones (lix, lx), Melonites for the fossil,
and Melonia for the recent forms. Defrance (xxix) proposed yet another. name, Ori-aria.
And finally M. D'Orbigny (lxix) adopted Bosc's name, with a slight alteration in its termi-
nation, which served at the same time to mark the continued existence of the type, and to
distinguish it from the Lamarckian genus of Corals. The name Alveolina was soon afterwards
adopted by M. Deshayes (xxx), and it may now be considered as the established designation
of the genus, the synonymy of which has recently been very fully treated by Messrs.
W. K. Parker and Rupert Jones (Lxxxa).

147. External Characters.- — The recent specimens upon which my investigations have
been made belong to a fusiform variety which was tolerably abundant both in Mr. Jukes's
Australian dredgings, and in Mr. Cuming's Philippine collection ; they were obviously identical
specifically, but those from the latter source considerably exceeded those from the former in
average size. The length of the longest complete specimen in my possession is '35 of an
inch ; but I have a specimen whose shape is nearly cylindrical (the A. Quoii of D'Orbigny),
which, though incomplete at one end, measures "50 of an inch. The ordinary form, from
which any considerable departure is very rare, is that which is exhibited in Plate VIII, fig. 13;
and it is obviously produced, as correctly stated by M. D'Orbigny, by the involution of a
spiral around an elongated axis. The surface is marked out by depressed septal bands into
a succession of segments of tolerably uniform breadth ; and each of these segments is crossed
by secondary furrows, which lie so closely together as to mark out each into a series of very
elongated areolae, that remind us of the oblong superficial areolae of the complex type of
Orbitolites (Plate IX, fig. 7), but are much narrower in proportion to their length. The
apertural plane of the spire is closed by a solid wall, the surface of which is nearly flat, and

* 'Bulletin des Seances de la Societe Philomathique,' No. CI.

100 FAMILY MILIOLIDA.

which is perforated by multiple rows of rounded pores, each surrounded by a prominent
annulus of shell, and bearing a very close resemblance to the pores at the margin of OrbicnJina
and Orbifolites. One such row is pretty uniformly to be made out at the inner border of each
apertural plane ; and another row of very small pores, closely set together, may be detected
in well-preserved specimens along the outer border. The apertural surface increases con-
siderably in breadth towards its two extremities, and the rows of pores are there more
numerous but less regular.

148. Internal Structure. — The internal structure of AJveoVma will be best understood by
supposing the cavity of an Oliva (or any other univalve shell that winds spirally round an
elongated axis) to be crossed not only by transverse partitions, which divide it into principal
chambers (indicated on the surface by the depressed septal bands that run parallel to the
axis), but also by a set of partitions at right angles to these, which divide each principal
chamber vertically into a row of long, narrow " chamberlets" in lateral contiguity with each
other, these secondary septa corresponding with the secondary furrows of the surface
(Fig. XXII). The chamberlets thus divided will open at the apertural plane by a single row

Fig. XXII.

Simple type of Alveoliim, as seen laid open at a, and in transverse section at B. At c is shown a portion of tlio apertural
plane of a specimen which exhibited two rows of pores ; and at d, a transverse section of one of the septa.

of pores resembling that which is characteristic of Peneroplis. It may occasionally be noticed,
however, that the septal pores form a double row, as shown at c ; in which case those
nearest the e.Kterior are directed towards the longitudinal canal, as is seen in section at D, a,
so as to establish a direct communication between each segment and the longitudinal
stolon from which the next appears to commence. Such is, in fact, the structure of all
the fossil Alvoolina I have examined ; and we may characterise it as that of the si'wple
type of Aheolina. — In the recent form which I have specially studied, however, the structure
is much more complex ; for each principal chamber is subdivided not only by vertical, but
also by horizontal partitions or floors, so as to form a succession of " storeys," which are
indicated externally by the multiplication of the rows of pores on the apertural plane. This
will be partly understood from Plate VIII, fig. 15, which represents a section of Aheolina
taken in the direction of its elongated axis, and which shows the general mode of increase by
successive convolutions around the primitive spheroidal chamber, each convolution extend-
ing considerably in a longitudinal direction beyond its predecessor, and thus adding much

GENUS ALVEOLINA. 101

more to the length than to the diameter of the shell. In this section the long narrow
chamberlets are divided transversely, so that they are merely seen as rows of rounded aper-
tures channelled out in the solid substance of the shell ; they correspond in relative situation
with the pores of the apertural plane, but are usually of much larger size. Generally about
four such rows may be distinguished in each convolution ; but they are far from being
regularly disposed, especially towards the two extremities of the axis of growth. Along the
outer margin of the last and of each preceding segment, we see a row of apertures much
smaller than the rest, and much more closely set together ; these are the transverse sections of
tlie superficial layer of chamberlets, the dimensions of which are indicated by the furrowing
of the surface, and which are about twice as numerous as those of the rows that lie internally
to them. This difference is peculiarly interesting when taken in connection, on the one hand,
with that which we have seen to exist between the superficial and the more deeply seated cham-
berlets of Fabularia (f 118), and on the other with that which we shall encounter between
the superficial and the intermediate" layers of chamberlets in OrbitoUfes (1 16G), the type in which
this differentiation seems to acquire its fullest development. The form and arrangement of
the chamberlets are better displayed by transverse sections of the shell, such as is represented
in fig. 14; in which figure the solid substance is left white, the shallow cavities occupied by
the sarcode (here laid open in the direction of their length) are shaded of a half tint, whilst
the black spots represent the openings of long galleries that pass continuously from one end
of the shell to the other, so as to bring all the chamberlets into free communication with each
other laterally. As each whorl is in regard to all essential particulars but a repetition of the
rest, it will be sufficient to describe the structure of the outer convolution. This is divided
into principal segments, which obviously correspond with the spaces that intervene between the
depressed septal bands of the external surface ; the places of those bands being marked, not
only by slight inflections of the external outline, but also by prolongations [a, a, a) of the
superficial lamella, which are directed inwards so as to contract the mouth of the spire at
what may be considered the termination of each formative act. Just within these projections
are seen the orifices [b, b, b) of one set of longitudinal channels, whilst nearer the internal side
of the convolution are seen the orifices {c,c, c) of another much larger series of longitudinal
channels, which are like galleries connecting the contiguous chamberlets of the same floors.
Between the orifices b, h, b, and the orifices c, c, c, which respectively correspond to them,
there is no division of the principal cavity of the spire into " storeys" of chamberlets ; but, to
carry out the analogy, those intervening spaces may be likened to the well-staircases by
which a vertical communication is established between the several " storeys" in a large
mansion. The principal cavity of each segment is elsewhere separated by the intervention of
three concentric laminae of shell {d, d^, d^) into a set of superposed chamberlets {e, e^, e^, e'),
which are usually four in number, though in a portion of the convolution that is rather narrower
than the rest we see only two lamellse and three chamberlets, whilst in a wider portion of
the interior convolution we see four lamellae and five chamberlets, and even this number is
frequently exceeded. The thickness of these lamellae is by no means uniform, and the capacity
of the chamberlets between which they intervene is subject to variation accordingly.
Generally speaking, the lamellae are thickest at their posterior extremities, so that the entrances
to the chamberlets from the vertical " wells" are there much narrowed ; in front of these
constrictions the cavities of the chamberlets usually open out considerably ; and they become

102

FAMILY MILIOLIDA.

narrower again towards their anterior extremities, where their terminations appear as the
pores on the apertural- plane whicli closes in each segment as its formation is completed.

149- The idea of the structure of the composite animal which we gain from the
examination of these sections of the shell is fully borne out by the examination of the
silicified " casts " of the interior, which Messrs. Parker and Rupert Jones have been fortunate
enough to obtain (p. 10) ; for these casts, which exactly represent the form of the sarcode-body
whose place they have occupied, exhibit just the arrangement and connections which might
have been predicated. The whole body (Fig. XXIII) is made up of a series of minute elongated
sub-segments, united together at their extremities, in the mode to be presently described, into
groups which represent the principal segments of Foraminifera of less complex type. Every
such group consists of several rows (usually four or more) of sub-segments, arranged vertically

Fig. XXIII.

Portion of an Internal Cast of an Alveolim of complex type -.—a, a, a, a, superficial series of sub-segments ;
b, I, b, subjacent series ; cc, cc, longitudinal stolons ; d, d, vertical columns.

one over the other ; but the sub-segments {a, a) forming the superficial layer are of only about
half the breadth of those [b, h) of the subjacent layer, and are about twice as numerous. The
superficial sub-segments spring by slender peduncles from a band or " stolon" (c, c) that passes in
a longitudinal direction from one end of the series to the other, and terminate at their anterior
extremity in a similar band. The sub-segments that form the subjacent layers spring
posteriorly by constricted necks from vertical " columns " {d, d) which occupy the " well-stair-
cases," and terminate anteriorly in similar columns ; and the columns forming each of the rows
that intervene between one segment and another are brought into lateral connection by two
or more " stolons " which pass along the entire series. Thus although the sub-segments
themselves have no direct communication with each other, they are intimately united into
one system by the intervention of these " columns " and " stolons." Looking to the place
of the connecting passages in the transverse section (fig. 14), it becomes obvious that the
stolons which occupy them are formed by the union of the pseudopodial extensions that
issue from the pores of the aperture. A coalescence of those proceeding from the four sets
of pores (one of them close to the inner margin of the spire) corresponding to each other

GENUS ALVEOLINA. 103

vertically along the septal plane in fig. 13, would establish what I have termed the "columns"
which seem to constitute the first-formed portion of a new segment ; a lateral coalescence of
these columns at tolerably regular intervals would establish the longitudinal " stolons ;" and the
formation of solid shell between these columns and stolons would leave them in occupation
of the two sets of communications that have been designated as the " well-staircases " and
the " horizontal galleries." The further development of the segment will consist in the
anterior extension from each " column" of a set of sub-segments of sarcode separated from each
other both vertically and horizontally by partitions of shell ; and the extremities of these will
appear, when the growth of the segment is completed, at the apertural pores, where they will
be again connected through the coalescence of their extensions, so as to form vertical
" columns" and longitudinal " stolons."

150. Varieties. — The foregoing plan of structure may be traced, with or without
modification, through a series of extinct forms which presents a wide range of variation in
shape, and which closely approximates at one extremity to that of Orbiculina. Thus the
(so-called) Orbiculina rofella of D'Orbigny (lxxiii, p. 140), notwithstanding its nautiloid
discoidal form, seems pretty certainly to belong rather to the Alveoline than to the Orbiculine
type of structure ; from this the transition is by no means abrupt to the oblately spheroidal
and thence to the spherical varieties of Alveolina melo, which is a very common fossil of the
early Tertiary Limestones both of the Continent of Europe and of India. From its spherical
we pass to its prolately spheroidal forms, and thence to its ovoidal (the A. ovoidea of
D'Orbigny), some of which last attain enormous dimensions, specimens being not unfrequent
in the Tertiary Limestones of Scinde whose length reaches three inches and whose diameter is
an inch and a half. A still greater elongation of the axis, with attenuation towards the extremities,
gives the fusiform shape of the A. Boscii, a variety which is common in the Paris Tertiaries,
and which bears a strong external resemblance to the one at present existing in tropical seas ;
and it is clear that the yet more elongated sub-cylindrical forms presented by A. elongata and
A. Quoii, of which the former is fossil and the latter recent, are nothing else than a result of
the tendency to elongation of the axis carried out to a still greater extent. There is, however,
an important difference in internal structure between the entire series of fossil forms and most
of their existing representatives ; for although the external aspects are so nearly identical in
certain specimens that they are only distinguishable by the difference in the number of rows
of pores in their septal planes, and although the general plan of the fossil is exactly con-
formable to that of the recent, yet that plan seems to be uniformly worked out in fossil
forms, however large may be their dimensions, upon the " simple" plan, the " complex"
being only met with in the type at present inhabiting equatorial seas. Noyv this
difference, being apparently well marked and constant, would obviously be entitled to rank
as of specific value ; if we did not find in Orbitolites, to which Alveolina is closely allied in
general plan of structure, that a difference of an exactly parallel character between what will
be there termed the " simple " and the " complex " types must be reduced to the grade of a
mere varietal modification, since the passage from the former to the latter is frequently
presented in one and the same individual.*

* It seems requisite for me to state, that I fiud myself unable to admit the existence of any

104 FAMILY MILIOLIDA.

151. JJfbnlic-^. — It will be obvious from what has preceded, that notwithstanding the
apparently wide interval which separates the typical Alveolina from its congeners, it has a
strong analogy both to Orhiculina and to Fabularia in its general plan of structure. Its
closest affinity, however, is evidently to the regularly spiral type of Orbiculina, since we find
in it no trace of that Milioline plan of growth which so remarkably characterises Fabularia.
It has been already pointed out that Orbiculina essentially differs from OrbitoUtes in the
investment of the first-formed convolutions by the latter, so that its umbilical region becomes
prominent instead of being depressed, and its spire coils round an axis instead of round a
point ; and, by tlie gradation which has been just shown to have an actual existence, the
progressive elongation of the axis round which the spire revolves converts the flattened
lenticular spiral of the J. rofella into the almost cylindrical volution of A. elonyata. The
difference in shape, in fact, is not nearly so great between Orbiculina adunca and A. roiella
as it is between A. rotella and A. ehnyata ; but it requires an examination which I have not
yet had the opportunity of making into the internal structure of A. rotella, to enable me to
affirm with certainty that the transition which it so obviously presents to the Orbicuhne
type in its external form extends also to its plan of growth.

152. Geographical Bidribufion. — The recent examples of this type are limited, so far as
we at present know, to the seas of tropical or southern temperate regions ; the larger
fusiform and cylindrical forms having been chiefly brought from the shores of New Holland
and of the Philippine Islands in the eastern hemisphere, and from those of Cuba and the
Antilles in the western ; whilst a small spheroidal variety, which appears to belong to the
simple type, is figured by Ehrenberg (xlii, pi. xxxvii, 10, fig. 1, a—f) from the Adriatic.

153. Geological Distribution. — The extinct forms of Alveolina belong for the most part
to the formations coeval with the Nummulitic Limestone ; and they present themselves in
various proportions, sometimes so abundantly as almost of themselves to make up the
substance of the deposit, in the early Tertiaries of Paris, Bordeaux, the Pyrenees, and
Austria, as also in those of Persia and Northern India (xix, xxi). One species is stated by
D'Orbigny (lxxiii, p. 145) to present itself in tlie Turonian or Lower Chalk formation at
the mouth of the Gironde, although none has been hitherto met with in any part of the
Senonian or Upper Chalk.*

" canaliferous system " in Alveolina ; and that the appearances which have been interpreted by
Mr. Carter (xxi) as indicative of its presence in the fossil Alveolina of Scinde are quite comforma'ble
with the account of its structure which I liave given on the basis of a very careful examination of that
of its recent analogue.

* I cannot agree with ray friends, Messrs. Parker and Kupert Jones (lxxx a), in referring tlie
Palffiozoic Fusulina to this type ; for although the metamorphic condition of the shell, in all the
specimens 1 have examined, forbids my speaking with full assurance, yet the appearance presented by
thin sections is such as to leave scarcely any doubt in my mind that its structure was tubular, and
that it consequently holds somewhat the same place in the hyaline series that Alveolina does ip the
porcellanotis .

GENUS ORBITOLITES. 105

Genus X. — Orbitolites (Plate IX).

154. Ilistori/. — The Orbitolile has been chiefly known, until very recently, rather by its
fossil than by its existing forms. The abundant occurrence of its disks in the ' Calcaire
grossier ' of the Paris basin early attracted attention ; but Orbitolites were not clearly distin-
guished by the older observers from Nummulites, and their true nature was entirely misun-
derstood. Thus we find them designated, often in association with Nummulites, under the
title of UmbiUcus marinm by Plancus (lxxxiii), who imagined them to be opercula of
Ammonites ; of Porpitce nummulares by Stobaeus and Bromell, who seem to have regarded
them as representing the disks of the existing Porpitae ; of Helicilcs and Operculites by
Guettard, who considered them as opercula of Gasteropods ; of BiscolUhi by Fortis, who
supposed them to be skeletons of Mollusks ; of Madreporites by Deluc, and of MiJleporites
by Faujas de St. Fond, whose idea of their nature is sufliciently indicated by the names they
assigned to them. (See i, § i.) The genus Orbitolites seems first to have been erected on
the type of the 0. coMplanafa of the Paris basin, and to have been differentiated from
Nummulites, by Lamarck (lviiJ, who ranked it between Lmmlites and Millepora, among his
" Polypiers Foramines." He subsequently (lx) altered the name from Orbitolites to Orbic-
Hies ; but the latter designation having been previously employed in Malacology, the first
appellation was restored by M. Milne Edwards in his posthumous edition of Lamarck's
work. Under one of the designations Orbilolites or Orbulites, the genus has been gene-
rally recognised by systematists (xiii) ; none of them, however, have either given any
account of its internal structure, or made any essential modification in the definition of the
genus ; and they all left it in the place which Lamarck had assigned to it, until after the
appearance of my own description of the microscopic structure of Orbitolites (xii), in which
I showed its identity with the recent Australian Maryinopora of MM. Quoy and Gaimard,
and of the subsequent memoir by Prof. Williamson (cviii), in which the Foraminiferous
character of this type w'as proved by the close conformity of its plan of organization to
that of Orbicnlina* It was not until the publication of his ' Cours Elementaire' (lxxiv)
in 18.52, that M. D'Orbigny admitted this genus into his systematic arrangement of Fora-
minifera ; the order Cyclostjigues, in which it is associated with Cyclolina (which I believe
to be only a variety of Orbitolites), with OrbiloUna (a generic type of quite a different
structure, to which I have thought it better to restore De Montfort's name Tinoporus), and
with Orbitoides (whose affinities with Cyclocli/pem and Kumiiiulilcs are of the most intimate
character), being then first created.

* It is due to Prof. Ehrenberg to state tliat he liad long before recognised this relationship
(xxxix) ; but by ranking Orbicidbia as well as Orbitolites among Bnjozoa, and by representing the
superficial cells in both types as occupied by eiglit-aruied polypes furnished with moveable opercula,
he so completely departed from the truth of nature, that it is not surprising that what was really correct
in his doctrines received little attention.

14

106 FAMILY MILIOLIDA.

155. External Characters. — The calcareous disks of Orbitolites (Plate IX, figs. 1, 7) vary
in diameter from about l-30th of an inch to ^-lOths of an inch ; whether large or small,
the}' are almost invariably circular or nearly so ; they are usually flat or slightly biconcave,
any difference in thickness being generally in favour of the marginal portion ; and if, as
sometimes happens, there is a slight central prominence (fig. 7, a), this consists only of that
first-formed portion of the shell which I shall describe as the " primitive disk" (^ 157), and
does not result (as in Orbiculina, ^ 135) from any overlaying of the original centre by subse-
quent growths of shell. Around this " primitive disk" we see an indeterminate number of con-
centric zones marked out by farrows of the surface ; and each of these zones is subdivided by
transverse furrows into a uniform series of areolae, which correspond with " chamberlets"
within. In the smaller specimens (fig. 1) these areolae are usually somewhat ovate in form,
their long diameter lying transversely to the radius of the disk ; in the larger specimens
(fig. 7), on the other hand, they have usually a narrow, rectangular shape, and their length lies
in the direction of the radius of the disk. This difference will presently be shown to be related
to an important diversity in internal structure. In those disks which have their surface
divided into ovate areolae (fig. 1), the margin presents a series of convexities with inter-
vening furrowed depressions ; whilst in the thicker disks (fig. 7) these are less regular and
less strongly marked. Unless the surface of the disk has been partially or entirely removed
by abrasion (as is often the case with dead specimens collected by dredging), it presents no
openings whatever, and the only orifices by which the interior of the shelly disk normally
communicates with the exterior are the pores (figs. 1, 7,f,f) that are seen upon its margin. Of
these pores, in the thinnest specimens (fig. 1), we find but a single one, or in some instances
two, lying in each of the marginal hollows ; in disks somewhat thicker we find each furrow
to contain three or four such pores ; whilst in the largest and thickest disks (fig. 7) the
number of pores occasionally rises to ten or even twelve. Thus, on the one hand, by the form
of the superficial areolae, on the other, by the singleness or multiplicity of the rows of
marginal pores, there is marked out a distinction between two types of Orbitolite structure
which have been accounted specifically or even generically different, but which, as they
frequently coexist in the same individual, have no title to be so regarded. It will be conve-
nient, however, to describe them separately, in the first instance, as the Simple and the
Complex types ; and to consider their mutual relationship subsequently. In both these types
the aspect of the shell much resembles that of Orhiculina, but has usually less of the opaque
whiteness by which it is characterised in that genus ; and sometimes, as in Orhiculina, the
surface is minutely punctated, giving a semblance of perforations, which, however, have no
real existence. In very thin specimens the calcareous laminae which form the two surfaces of
the disk are so translucent that, when such specimens are mounted in Canada balsam, the
chambers they enclose can be clearly made out. Moreover, even in larger specimens which
have been collected alive, and which consequently contain the animal body in a desiccated
state, the translucency of the shell allows the crimson hue of the sarcode to be seen through
it, so that the whole disk seems to be tinged by this, although the proper substance of the
shell, when examined by transmitted light under a sufficient magnifying power, is found to
present the brownish-yellow hue characteristic of the Milioline type.

GENUS ORBITOLITES. 107

156. Simple Type : External Characters. — In sands and dredgings brought from the seas
of any of the warmer regions of the globe, and especially in those from the Philippine shores,
we almost constantly meet with an abundance of minute Orbitolite-disks, whose diameter is
ordinarily about '05 of an inch, and which usually contain from ten to fifteen concentric zones.
These constitute the OrhiloKtes marginalis of Lamarck (lx), the Sorites orbicuhs oi Ehren-
berg (xxxix). Although these disks are typically plane or nearly so (there being usually
no great difference between the thickness of their central and that of their peripheral region),
yet it not unfrequently happens that the successive zones gradually increase in thickness
from within outwards (as is shown in Plate IX, fig. 2), so that the disk becomes somewhat
biconcave. Sometimes, again, without any alteration in the thickness of the several parts,
the disk comes to assume, by the depression of its central portion, the shape of a plate, or
that of a watch-glass, or (by the more complete upturning of its edges) that of a saucer.
In any case in which either surface of the marginal zone is more exposed by its projection
than those of the zones which it encloses, there will be a special liability to a laying-open of
its chamberlets if the disk should be subjected to attrition ; and I doubt not that in this
mode have been produced the supposed large pores of the fossil 0. macropora, the figure of
which given by Goldfuss (' Petrefacta,' pi. xii, fig. 8) corresponds exactly with recent specimens
I have frequently encountered, presenting a row of large ovate apertures along the surface
of the outermost zone. The true pores (which have been very commonly overlooked) are
situated in the depressions between the marginal convexities (Plate IX, fig. 1,/,/) ; in each
of these depressions there is but a single pore, and this is almost always of a regularly
circular form, and is surrounded by a prominent annulus of shell.

157. Internal Structure.— When the interior of an Orbitolitcs of simple type is laid open
by a section that passes in a direction parallel to one of its surfaces (which in the case of
these discoidal forms will be most conveniently termed a horizontal section), as shown in
Fig. XXIV, the central portion is seen to be occupied by a large cavity, that is somewhat
irregularly divided by a sinuous partition ; notwithstanding some irregularity, this partition
always marks out a " primordial chamber," a, of a somewhat pyriform shape, from the
" circumambient chamber" b, b, which passes round it ; in this partition there is an aper-
ture, d, which establishes a communication between the narrow prolongation of the " pri-
mordial" or " central" chamber and the large " circumambient chamber." (See also Plate IX,
fig. 1.) The meaning of this arrangement will at once be made apparent by reference to
the disposition of the " primordial" and " circumambient" segments of sarcode, which occupy
the cavity of what may be conveniently termed the " primitive disk" (^ 161). In a vertical
section passing through the centre of this disk, such as that seen in Plate IX, fig. 2, it seems
to present three chambers ; but this is simply due to the fact that such a section will traverse
the circumambient chamber twice, that is, will cut it through on both sides {b, b) of the
central chamber a. Some sections present only two such chambers ; in this case the plane
of division seems to have traversed the "primitive disk" just where the neck of the
primordial chamber touches its margin, so that the circumambient chamber is only on
one side of it. If, on the other hand, the plane of division should happen not to pass
through the primordial chamber at all, so as to traverse the circumambient chamber
alone, a single broad cavity will present itself in the vertical section, as shown in fig. 8, b.

'108

FAMILY MILIOLIDA.

Frequently, however, it happens that the circumambient chamber is partially subdivided on
one side by an interposed partition (Fig. XXIV) ; and then a vertical section will show /o?er
chambers, the central chamber having the undivided part (i) of the circumambient chamber
on one side of it, and the divided part {li, b') on the other. Each zone, as seen either by
transmitting light through the thinnest and most translucent specimens after mounting them in
Canada balsam, or by making horizontal section of thicker specimens, consists of a circular set
of small ovate cJiamherkfs [c, c, Fig. XXIV, and Plate IX, fig. 1), excavated, as it were, in the

Fig. XXIV.

Diagrammalic ix-prcseutation of the anterior of an Orbiloliies of simple type : — a, primordial chamber ; b, h, circumambient
chamber ; b', portion of the same partially separated by an incomplete partition ; c, c, c, chamberlets of the concentric
annuli ; d, passage from the primordial to the circumambient chamber ; e, e, e, passages from the cireumambieut cham-
ber to the chamberlets of the first annulus; /,/,/, passages from the gallery of the last anuuhis, opening at the
marjin of the disk.

shelly substance of the disk, and communicating with each other laterally by annular passages
which unite them together into a continuous gallery. The zone which immediately surrounds
the " primitive disk " is connected with it by radial passages (Fig. XXI, e, e), which extend
from the outer margin of the large circumambient chamber to the several chamberlets of
which that zone is composed ; and each zone communicates with the one on its exterior by
similar radial passages (Plate IX, fig. 6, e, <•), which usually extend, however, not from the
chamberlets of the inner zone to those of the outer, but from the annular passage {li, h) of
the inner zone to the chamberlets of the outer ; and thus it comes to pass that the cham-
berlets of each zone usually alternate with those of the zones that are internal and external
to it. — A vertical section of the disk, such as is shown in Plate IX, fig. 2, exhibits the same
arrangement under a diflferent aspect. The chamberlets c, c, c of the concentric zones are

GENUS ORBITOLITES. 109

seen to be much higher than they are broad, so that they present a somewhat coUimnar
form ; the proportion of their height to their breadth, however, may vary greatly in different
parts of the same disk, the former often increasing from the centre towards the periphery,
whilst the latter remains constant, or nearly so; and the columns, instead of being straight,
are generally more or less curved, and are sometimes bent in the middle at an obtuse angle.
The gradation which presents itself from one of these forms to the other, and their coexist-
ence even in the same specimens, clearly prove that no value can be attached to the form
and proportions of the chamberlets, thus seen in a vertical section, as furnishing specific
characters. In every perfect specimen the columnar chamberlets are seen to be closed at
their two extremities by a thin wall of shell ; and this is sometimes flat, sometimes more or
less convex.

158. In this manner any number of concentric zones may be formed, which are exact
repetitions of each other, except that the number of chamberlets in the outer zones is greater
than that of which the inner zones are composed. It does not increase, however, in the
regular ratio of the respective diameters of the zones ; for the chamberlets of the outer
zones, being usually both larger and more widely separated from each other than are those of
the inner, are less numerous in proportion ; thus, in a specimen before me, there are twenty-
eight in the innermost row and only forty-nine in the outermost, though the latter is more
than twice the diameter of the former. The augmentation in number is accomplished by
the occasional interpolaiion of an additional chamberlet, communicating directly with the
one immediately interior to it, between the two chamberlets which are connected with the
annular passage on either side of the latter, as is shown in Plate IX, fig. 6, c' , c". The
chamberlets of the last-formed zone communicate with the exterior by the same kind of
radial passages as in other instances communicate with the next zone ; and the external
orifices of these form the pores which present themselves at the margin of the disk (Plate IX,
figs. 1, 2,/,/). Thus it is seen, on the one hand, how it happens that these pores are
intermediate between the chamberlets, instead of opening directly into them ; and on the
other, how each pore leads, by the divarication of its passage, into two chamberlets, one on
either side of it. When a new zone is formed, each pore opens into one of its chamberlets ;
and this zone, in its turn, communicates with the exterior through a new set of pores at its
own margin. When the section passes through the prominent annulus of shell which
surrounds each pore, this will be indicated by a little " beak" on either side of the entrance
to the passage ; such " beaks" (which are, of course, repeated through the entire disk)
are shown in their ordinary aspect in Plate IX, fig. 6, /, /), but they are frequently
more prominent. In all cases in which the growth of the disk takes place with
normal regularity, a complete circular zone is added at once. Exceptions to this regu-
larity are rare, and they can be generally traced with probability to some accidental
interruption.

1 59. It is a fact of much importance, in the due appreciation of the relations of
Orhilolifes to other types of Foraminifera, that the calcareous partition which separates each
chamberlet of any one zone from the adjacent chamberlets on either side is not double, but
siyic/le. And this is in great part the case, even with regard to the partitions which separate

110 FAMILY MILIOLIDA.

the chamberlets of successive zones, the inner or central boundary of one being chiefly
formed by the peripheral wall of the other. It is not easy, even in thin sections, to distin-
guish the boundary between the walls of one zone and those of another, so absolutely
continuous do they appear to be. But it not unfrequently happens that, in fracturw(i these
disks, their component zones come apart from each other along their natural lines of junc-
tion, so as to disclose the real inner margin of the outer zone (Plate IX, fig. 1, g, (/), which is
then found to present a set of wide fissures, through which we look at once into its cham-
berlets, thus proving their incomplete enclosure by proper walls on that side.

1 60. There cannot be any reasonable doubt that the number of concentric zones which
any disk may present is entirely determined by its stage of growth, and that it aftbrds no
basis whatever for specific distinction. Just as in the case of the concentric layers of wood
in the stem of an exogenous tree, a minute " primitive disk," surrounded only by a single
annulus of chamberlets, may come in time to be the centre of a large disk consisting of
many scores of concentric zones. Although, as already stated (^ 156), most of the Orbi-
tolites formed upon this simple type are of comparatively small size, yet there does not seem
to be any definite limit to the multiplication of zones ; for I possess specimens attaining '25
of an inch in diameter, and consisting of about fifty zones (much larger, therefore, than the
younger disks of the complex type), in which there is no appearance of any departure from
the original mode of growth.

161. Structure of the Animal.— The; entire animal body, obtained by the decalcification of
the shells of specimens that have been taken alive and preserved in spirit (Plate IV, fig. 14),
is composed, of a numerous assemblage of minute segments," arranged at tolerably regular
intervals in concentric zones, around what it may be convenient to term the " primitive
mass." This primitive mass consists of a pear-shaped " primordial segment" (Plate IV,
figs. 1 6 — 20, a) occupying the central or primordial chamber, from the small extremity of
which a peduncular process [d) extends, that dilates again into the still larger segment h, b,
which, from its almost completely surrounding the former, may be conveniently designated
the " circumambient segment." Thus, the " primitive mass" very closely resembles what the
body of a young Miliola would be, if the segment first budded-oft" from the primordial
segment were prolonged, so as completely to surround it (1 49, Plate IV, fig. 4, b). From
the outer margin of this circumambient segment there radiate a number of slender pedicles
(c), which presently enlarge into as many columnar segments, having a circular or oval base,
and these are united to each other laterally by a connecting band or " stolon" {h, h), which
passes entirely round the " circumambient segment" and forms a complete annulus. It is
usually from the portions of this "stolon" which intervene between the segments of each
annulus of sarcode, that the radiating pedicles (fig. 23, e, c, e) are given off, which go to
originate the next zone ; but sometimes a pedicle is given oft' from one of the segments (as
shown at e',e'), which goes to form a segment (c", c") in the next zone, that is interpolated
between two which have originated from the intervening annular stolon ; and it is in this
manner that the numJjer of segments in successive zones receives an increase, the size of those
segments not undergoing any considerable augmentation. Each successive zone exhibits
precisely the same structure ; and it is obvious that the radiating pedicles of the outermost

GENUS ORBITOLITES. Ill

zone will issue from the marginal pores, and will give origin to the pseudopodia by whose
action the life of the entire composite organism must be sustained. The analogy of other
Rhizopods would lead us to suppose that it is by the introduction of alimentary particles
(chiefly minute forms of vegetation), through their means, into the mass of sarcode of which
they are extensions, that the fleshy body pervading the entire disk is nourished. For
although there is nothing like a digestive cavity in any part of it, or an alimentary tube
passing from one portion to another, still less any vascular communication between the
segments, yet as the sarcode forms one soft homogeneous mass everywhere continuous, the
body as a whole will receive the benefit of any incorporation of new matter with its substance,
in whatever situation this may be made. That organic particles small enough to pass
through the marginal pores are thus introduced into the chambers of the disk, is proved by
the curious fact that the residuum left after the decalcification of large and therefore aged
disks, whose animal contents have not been preserved, consists almost entirely of an
assemblage of remains of minute Diatomacca, Desmidiece, &c., which have obviously been
retained in the interior of their cavities after the assimilation of the nutriment they were
competent to afford. The sarcode-body of the animal, growing at the expense of the nutri-
ment thus appropriated, will gradually, it is probable, project itself through the marginal
orifices, not merely in filamentous pseudopodia, but in quantity sufficient to form a new zone;
and it is easy to understand, from the analogy of other Foraminifera, that such extensions will
coalesce with each other laterally, so as to form a complete annuhis around the entire
periphery of the dislc. This, at any rate, must be the case when a new zone is to be added to
the shell ; and it would seem as if this annulus then undergoes a thickening into segments by
the accumulation of sarcode at the points at which it receives the radiating pedicles from the
last zone of the sarcode-body included within the shell, whilst it becomes narrowed in the
intervening portions, which form the connecting bands between the segments. It may be
presumed to be by a calcareous exudation from the surface of this beaded ring of sarcode,
that the formation of the new shelly zone is accomplished ; and if the calcifying process com-
mence on the segments, and extend from these along the surface of their connecting stolons,
we can understand why the passages that are left for communication with the exterior should
arise from the intermediate divisions of the annular canal rather than from the segments
themselves. — Although the body of the animal is so far decolorized in the spirit-specimens
which alone have hitherto come under my observation as to present only a brownish hue,
yet as specimens that have been gathered fresh and have been then dried possess a reddish
aspect, which is due to the desiccated body they contain, it may be presumed that the
sarcode of the living Orbifolites has the same bright-red colour as that of Botalia and many
other Foraminifera.

162. I have not met with the least indication that the sarcode is contained within any
prosier membrane ; and the absence of any such indication, notwithstanding the various
manipulations to which I have subjected its segments, may be taken, I think, as strong
negative evidence that it has no more existence in this animal than it has in the species ot
Foraminifera whicii have been so well studied by M. Dujardin and Prof. Schultze. Nor is
there the slightest trace of distinct organs, either in the mass of sarcode which forms the
"primitive mass" or in that which constitutes each one of the surrounding segments; and

112 FAMILY MILIOLIDA.

he would, I tliink, be a mere speculator who should maintain the presence of a digestive
cavity in any of these parts, or the existence of an intestinal canal in the peduncular threads
which connect them together. The homogeneity of the component substance of the
"primitive mass," and of the entire assemblage of multiple segments, seems, indeed, to be
conclusively established by the following facts : — In all the spirit-specimens which I have
examined, the cavities of the outer zones are completely void, whilst those of the " primitive
disk" and of the inner zones are quite filled with their animal contents. This drawing
together of the soft body towards the centre is evidenced also in many of the larger specimens
which have been dried when collected in the living state, by the limitation of the red colour
that indicates tlie presence of the sarcode to the inner portion of the disk. In both cases it
may be presumed that the animal matter has shrunk together, in the former through the
corrugating action of the spirit, in the latter through desiccation. Now if the " polypidom"
of a Zoophyte or the " polyzoary" of a Polyzoon be similarly treated, there is no such
drawing together of the entire body, but each cell is found to contain the shrunk contents of
its own zooid ; and this difference seems to me to indicate a complete dissimilarity in the
characters of the two kinds of organisms. For it is obvious that the substance of the
peripheral segments of the Orbitolite-body can only be brought together towards the centre,
through being completely unattached to the walls of the cavities which it occupies, and
through having a form so alterable as to be capable of being drawn in threads through the
narrow connecting passages, and of then coalescing together again so perfectly that the masses
they form do not present the least trace of having been thus spun out. There is no known
kind of animal texture except sarcode that is susceptible of this kind of alteration ; and the
evidence of it which I have adduced seems to me extremely valuable, not only as establishing
the general nature of the animal body of Orbitolites, but also as fully justifying the assumption
that, in the living state, the sarcode is projected in pseudopodia through the marginal
apertures, and that alimentary particles are introduced by their instrumentality, as in other
Foraminifera.*

163. Complex Type: External Characters. — From the simplest it will be convenient
to pass at once to the most complex type of structure presented by Orbitolites, the existence
of which is marked externally (as already noticed, ^ 155) by a multiplication of the ranges of
marginal pores. I have met with this form in specimens obtained by dredging from the
coast of Australia and from various parts of the Polynesian Archipelago, from the neighbour-
hood of the Philippine Islands, from the Red Sea, and from the J^gean ; and as the sands of
all these localities present the simpler type in great abundance, I am disposed to believe that
the former is really not the less widely diffused than the latter, and would be discovered
wherever it abounds, if properly searched for. The largest specimen in my possession,
measuring 7-lOths of an inch in diameter, is from the coast of Australia, where these
Orbitolites are so abundant at certain spots (as I learn from Mr. Jukes) that their entire

* I tliiuk it desirable to repeat what I have already (xiii) stated upon this point, since the per-
sistence of Prof. Ehrenberg in his affirmation of the Bryozoic nature of these organisms might induce
those who rely on his authority to accept his figure of their animal (xxxis) as the representation of a
fact, instead of being merely the expression of tlieir author's idea.

GENUS ORBITOLITES. 113

disks and fragments, with fragments of Corallines (chiefly, I believe, the Corallina palmata of
Ellis), constitute the great mass of the dredgings. Among the Australian specimens several
attain a diameter of "-^S inch, and a considerable proportion as much as '30 of an inch.
Hence the Orbitolites of this type are among the largest forms of existing Foraminifera, being
only surpassed, as far as I am aware, by the Cyclochjpeus hereafter to be described. Of two
specimens in my possession from the Fiji Islands, one measures '63 inch, and the other -53
inch in diameter ; but the average of the Polynesian specimens seems to be considerably lower
than that of the Australian, as their diameter seldom exceeds -25 of an inch, and is usually
not more than 10 or -12.

1 64. The disks formed on this plan, like the preceding, may be considered as typically
circular, although they are seldom or never exactly so in reality. They may be considered,
too, as typically flat, with a slight concavity in the central part, from which, however, the
primitive disk often projects ; but, as will hereafter appear, there is no constant relation either
between the thickness and the diameter of different specimens, or between the thickness of
different parts of the same specimen and the distance of these parts from its centre. The
only remarkable departure from the ordinary form which I have met with, presents itself in
certain Orbitolites from the Fiji Islands, of which several specimens in the Museum of the
Royal College of Surgeons, and two in my own possession, exhibit a curious plication towards
their margins ; the degree of this departure varies so much, however, in different individual?
(the plication being almost obsolete in some), that it cannot be admitted to mark a specific
diversity. These same specimens, moreover, also exhibit another curious abnormality ■
namely, the projection of the upper and lower edges of the margin, so that a groove is left
between them, the projecting laminae being thin and fohaceous, and their chamberlets very
irregularly arranged. This peculiarity, again, being far from uniform in its degree, and being
altogether wanting in specimens which in other respects precisely resemble those with plicated
and foliated margins, must be considered merely in the light of an accidental variety ; but I
cannot suggest any explanation of its occurrence, or of its limitation (so far as I am aware) to
this particular locality.

165. The surface of the disk (Plate IX, fig. 7)* is marked out, as in the simpler type, by
concentric zones, the number of which bears a general (though not a constant) ratio to its
diameter; these zones are traversed by radiating lines, which mark out areolae that are
usually somewhat rectangular in shape and sometimes approach a square, but are more com-
monly nearly twice as long in the line of the radius of the disk as they are in the transverse
direction, their long sides being nearly parallel to each other. We shall hereafter see, however,
that the form of these areolae is very subject to variation, and that it may be very dissimilar'

* In order to avoid a multiplication of figures, I have thought it preferable to combine in three
ideal representations (Plate IX, figs. 7, 8, 9,) the details I have made out from a great number of
preparations which are faithfully represented in separate figures accompanying the original Memoir in
the Arcliives of the Royal Society ; these last of course furnish the real authority for every point in the
description, the ideal figures, however, serving to display the relation of different parts to each other
in a manner that no single preparation would possibly admit.

15

114 FAMILY MILIOLIDA.

even in different zones of the same disk (^t 173, 178). The pores /,/ at the margin of the
disk are disposed, as in the simpler type, between the projections formed by the convexities of
the chamberlets ; but they are less regularly circular than in the simple type, and the sur-
rounding annuli of shell is less distinct. The number of pores in each vertical row
is by no means constant, even in different parts of the margin of the same annulus; and their
disposition is far from regular (fig. 10), as they seldom form rows that seem exactly con-
tinuous with each other horizontally, while the vertical rows are often interrupted, the two
adjacent rows then usually inclining towards each other.

166. Internal Structure. — The disks of this complex type are not distinguished from
those of the simple type already described, by any difference in the structure of the
" primitive disk ; " and there is frequently nothing specially characteristic in the structure of
the zones that immediately surround it. Each of the peripheral zones, however, consists of
two superficial layers, and of an intermediate stratum (Plate IX, figs. 7, 8, 9) ; these will now
be described seriatim. The superficial layers are formed of the (usually) oblong chamberlets,
whose contour is indicated by the surface-markings ; when they are laid open horizontally,
by rubbing away the thin shell which covers them in (fig. 7, i, i, i), it is seen that the
floor of each chamberlet has an aperture at either end ; but no communication can be
traced, either through the side-walls between the contiguous chamberlets of the same zone,
or through the end-walls, between the chamberlets of successive zones. Moreover, there is
no such alternating arrangement of the chamberlets of successive zones, as we have seen to
prevail in the simpler type (^ 157) ; and they altogether seem to be quite independent one
of another. When this superficial layer is examined in a vertical section having a radial
direction (Plate IX, fig. 8), it is seen that the floors of its chamberlets are formed by the
expanded summits (/, /,) of the irregular septa which separate from each other the successive
zones of columnar chamberlets of the intermediate stratum {r, c, c', c,) ; and that the
apertures at the two ends of the floor are the entrances to passages (w, ;«'), which lead
obliquely downwards (the passages on either side of the partition between two successive
chamberlets of the superficial layer always inclining towards each other) towards these
cavities. It is observable, moreover, that just at the point at which the contiguous passages
meet each other, there is always a round aperture (//, //) in the partition which divides the
contiguous chamberlets of each zone; and when, in a horizontal section, the superficial
chamberlets have been entirely ground away, so as to lay open the most superficial part of
the intermediate stratum, this part is found to be traversed in each zone by a continuous
circular gallery (Plate IX, figs. 7, 9, /i, //,//.,) with large rounded openings that lead into the
columnar chamberlets beneath. The meaning of this arrangement becomes obvious, when
We examine the disposition of the animal substance which occupies these cavities ; for we
find, as might have been anticipated, tliat the superficial cells are filled with segments of
sarcode of corresponding shape (Plate IV, figs. 24, 25, a, a'); and that whilst these have
no direct connexion with one another, each of them is connected by means of fleshy
peduncles with the annular stolons d, b' that run along its extremities ; whilst from the under
side of these annular stolons (fig. 25) descend the thick columns of sarcode {ce, c'c), which
occupy the columnar cells of the intermediate stratimi. The absence of any essential
dependence of the segments of the superficial and of those of the intermediate strata upon

GENUS ORBITOLITES. 115

each other, seems indicated by the fact that there is no constant numerical relation between
them, — a circumstance which extremely perplexed me, until I had ascertained, by exami-
nation of the animal, that the passages proceeding from the former (Plate IX, fig. 8, in, ?«')
debouch, not (as I had at first supposed) into the columnar chamberlets c ,c', but into the
annular canals, //, U , which serve to bring the superficial and columnar segments of each
zone into mutual communication.

167. As the description now given of the superficial layer applies equally to both
surfaces, we may now proceed to the intermediate stratum. When this is laid open by a
horizontal section (Plate IX, figs. 7, 9), it is seen to consist of a series of concentric zones,
the chamberlets of which alternate with each other, like those of the Simple type (^ 157).
The chamberlets are usually cylindrical (or nearly so) in form ; but often differ considerably
in size in different parts of the same disk, and sometimes even in different parts of the same
zone. It may be often observed that the cylindrical cavities do not always pass from end
to end in a straight line (Plate IX, fig. 11); nor do they always maintain a complete isolation
from each other, an inosculation of two columns (which is indicated in vertical sections
like that represented in Plate IX, fig. 8, by irregularly disposed apertures) not being unfre-
quent, while more rarely there is a fusion of two columns into one. All these features of
structure presented by the shell, are beautifully displayed by the animal (Plate IV, fig. 25) ;
the columns of sarcode c c, dc exhibiting the generally cylindrical form, the not unfrequent
inosculation, and the occasional fusion, which we have seen to exist in the cavities which
they occupy. At their upper and lower extremities, they unite with the annular stolons
JjJj , hU , which pass continuously round, in each zone, between the intermediate and the
superficial layers.

168. Save in the case of such accidental inosculations as those just noticed, no other
lateral communication seems to exist between the contiguous chamberlets of the same zone,
than that which is established by the annular stolons just mentioned. The chamberlets of
the successive zones communicate with each other, however, as in the Simple type previously
described (^ 157), but with a curious modification; for whereas a horizontal section of the
latter shows that each chamberlet communicates with the two chamberlets alternating with
it in the interior zone (Plate IX, fig. 6), a hke section of the Complex type seems to show
that such a connexion exists with only one chamberlet of the interior zone, by a passage
running obliquely from one to the other, and extending continuously through several succes-
sive zones (Plate IX, figs. 7, 9, e, e), the very same section exhibiting opposite obliquities in
contiguous parts. The study of vertical sections, however, made tangentially instead of
radially, so as to cross these connecting passages, shows the explanation of tbis apparent
anomaly to be simply as follows. Each cylindrical chamberlet really communicates with
the two alternating chamberlets in the next interior zone, but by two distinct passages,
instead of by the divarication of one ; these inter-zonular passages are not upon the same
plane, but those of different planes are directed alternately towards one side and the other ;
and thus, as the disks are seldom perfectly fiat, the section which traverses, at one part of
the disk, the set of passages running in one direction, will traverse the other set of passages,
where, by the flexure of the disk, the plane of section is slightly altered in regard to it. So

116 FAMILY MILIOLIDA.

the marginal pores of any one vertical row, even when in a line with each other, open alter-
nately into the chamberlets on the rifjld and on the left of that row ; these pores being
nothing else than the orifices of the oblique inter-zonular passages, which, when another
annulus is added, will lead into its chamberlets. The import of this arrangement is at once
made evident by an examination of the segments of the animal body that occupy the cylindrical
chamberlets ; for, as is shown in Plate IV, fig. 25, each column of sarcode in one zone (c c)
communicates with the two columns alternating with it in the next zone {c'c) by two rows
of peduncles ; and the peduncles which pass from each pair of contiguous columns to the
single column of the next zone, incline towards one another, so as to enter it nearly in the
same vertical line, though in different horizontal planes.

] 69. That which has been already stated in regard to the partial deficiency of the inner
wall in each of the concentric zones of the Simple type (^ 159), holds good also in regard
to the septa which divide the successive zones of the "intermediate stratum" in this more
Complex type ; for the walls of the cylindrical chamberlets close-in around them very imper-
fectly on their inner or central side, leaving large irregular vertical fissilres (Plate IX, fig. 11)
which are applied to the vertical rows of orifices (fig. 10) on the outer margin of the included
zone.

170. The thickness of this "intermediate stratum," and the number of superposed
segments (indicated by that of the inter-zonular peduncles) of which each column of sarcode
consists, are found to vary considerably in different parts of the same disk ; being usually
least near its centre, and gradually augmenting in successive zones as their distance from
this increases (Plate IX, fig. 8) ; or ceasing to augment at a certain point, so that the outer
part of the disk is flat ; or even diminishing again, so that the disk thins away towards its
margin. It is specially worthy of note that whatever differences of this kind may exist, they
are entirely due to the variable length of the columns of the intermediate stratum ; the depth
of the chamberlets of the si'jjerficial layers being nearly constant, and no vertical multiplica-
tion of these ever taking place.

171. The addition of new zones usually takes place Avith the same regularity in the
Complex as in the Simple type of structure ; but departures from this regularity, occasioned
by a want of completeness of particular zones, are more frequent ; and this is perhaps to be
accounted for by the larger size of the disk, which will tend to produce a less intimate
dependence of each part of the animal body upon every other, and will thus favour the
partial action of any cause {e.g. an excess of nutrient materials) which promotes a more
rapid growth on one side than on the other. And this view is most remarkably borne out
by the fact, that in the genus Cychchjpeus, which, though normally growing upon the cyclical
plan, possesses a much greater degree of segmental independence, such irregularities occur
far more frequently ; so that, in fact, it is rare in that type to meet with a disk whose increase
has taken place with uniformity throughout.

172. The foregoing description apphes in every particular to those specimens only,
which present the structure of the Complex type of Orbitolifes in its most regular and charac-

GENUS ORBITOLITES. 117

teristic development ; and the differences between this and the Simple type previously
described are such as at first sight to preclude the idea of their specific identity. But when
a large number of specimens are carefully examined and compared with each other, it
becomes obvious that not only may a vast amount of diversity present itself in the arrange-
ment of the chamberlets of the shell and of the segments of the animal,— so that one after
another of the characters which at first seem most clearly marked and therefore most
distinctive, may be shaded off" (so to speak) in such a manner as to establish a complete
transition between the two types, — but they frequently coexist in the very same disk. Such
a ^coexistence is exhibited in the vertical section represented in Plate IX, fig. 8, where we
see that the zones b — k, which immediately surround the "primitive disk," are formed in all
respects upon the Simple type ; between k and « we see an incipient diff'erentiation between
the " superficial " and the "intermediate" strata, the annular canal, however, still remain-
ing single ; but at n, the annular canal becomes double, and from this point to the margin
of the disk we see the " superficial " layers completely diff"erentiated from the " intermediate,"
and the former becoming more and more widely separated from each other by the increasing
thickness of the latter. Now as the Complex type of growth may show itself in the very
first annular zone, or may thus evolve itself out of the Simple at any distance from the
centre, and this either suddenly or gradually, it seems obvious that between these two types
no essential distinction can exist. If the growth of such a disk as that whose vertical
section is represented in fig. S, had been stopped at k, or even at n, it would have
undoubtedly been regarded as belonging to the Simple type ; and every disk formed upon
the Simple type must be considered as having the power to evolve itself upon the Complex
plan. It would not be right, however, to afiirm that the Simple disks are the young of the
Complex, since we find that the former may continue to increase without change, until
they far exceed in diameter and in number of zones the smaller disks which have early
assumed the latter type. Of the conditions which determine the original evolution of the
Simple or of the Complex type respectively, from "primitive disks " which appear to be in
all respects identical, or which determine the evolution of the latter from the former, we
know nothing whatever.

173. Even where the annular canals have been separated from each other, and a
distinct " intermediate stratum " has been formed between them, the superficial chamberlets
are not always clearly marked off" from its cylindrical cavities ; for instead of being separated
by floors formed by the expanded summits of the zonal septa (^ 166), they sometimes open
at once into the chamberlets of the intermediate layer, so as to be quite' continuous with
them ; and this continuity of the superficial with the intermediate chamberlets is sometimes
maintained throughout the disk, so that in no part of it are the former clearly marked off"
from the latter. This method of growth is so remarkably constant in the fossil Orbitolites
of the Eocene strata, whose intermediate layer is fully and very regularly developed, that it
might be considered to be specifically characteristic of them, did we not occasionally find it
to occur in certain zones of recent disks, which are elsewhere exactly conformable to what J
have described as the regular type. Where the superficial chamberlets are continuous with
those of the intermediate substance, they present the rounded or ovoidal shape, instead of
the elongated straight-sided figure which is their characteristic form ; and the former seems

118 FAMILY MILIOLIDA.

to give place to the latter, whenever the chamberlets of the superficial layers are perfectly
separated from those of the intermediate stratum, and are connected only with the annular
passages.

174. The "intermediate stratum," again, may be altogether wanting, notwithstanding
that the two superficial layers are separated from each other by a horizontal partition. In
this case, each layer may have its own annular canal, or there may be but a single canal,
which is then genei'ally very large ; and the chamberlets of the two layers have an alternating
arrangement as regards each other. Such an arrangement may present itself as one of the
modes of transition from the Simple to the Complex type, the cylindrical chamberlets
being disposed to subdivide transversely when they attain a considerable length, and the
annular canal to become double ; whilst in zones more distant from the centre, the two
layers are separated by the interposition of the intermediate stratum. Sometimes, however
the disk continues to increase and attains a considerable size on this duplex type, as we see
especially in the Orbitolites of the Red Sea ; and its edge then presents two rows of rounded
prominences with pores between them, those of the upper and lower rows alternating with
each other. It is on a dislc of this type that Prof. Ehrenberg has founded his genus
Amphisorus (xxxix), which I cannot regard as even specifically distinct from the ordinary
Orbitolik's. — There is sometimes a complete absence of regularity in the disposition of the
cylindrical chamberlets of the intermediate stratum, so that they present an assemblage of
indefinitely-shaped passages, communicating with each other in various directions. This
variety is chiefly interesting, as showing how little importance is to be attached to smaller
deviations of the same kind. Further, the septa dividing the contiguous chamberlets of the
same zone are occasionally deficient, so that the interior of the zone is a continuous circular
gallery, with only slight indications of the normal divisions ; thus corresponding exactly with
the peneropliform condition of Orhicidina (^ 143). In such a case, it is obvious that the
ring of sarcode must have been everywhere of nearly uniform thickness, showing no division
either into horizontal or into vertical segments; and it may not be thought improbable that
this is its first condition in every case, and that its segmental division is a subsequent process,
so that the shelly investment, if formed previously to the segmentation, will have the
character of incompleteness just described. I cannot lielp suspecting, that the peculiar
groove around the margin of the Fiji specimens formerly noticed (Ij 164), is referable to a
still greater incompleteness of the production of the calcareous investment around the newly-
formine zone.

'&

175. Reparation of Injuries. — Much light is thrown on the physiology of the Orbitolite
type of structure, by the examination of specimens — of which I have met with several —
whose conformation makes it evident that, after larger or smaller portions of the disk had
been broken away, a new growth has taken place along the fractured edge. Two examples
of this are shown in Plate IV, figs. 26 and 27. — In the first of these, it is obvious that so
large a portion of the disk has been broken away, as to leave only an irregular fragment,
including its centre and about an eighth of its margin. Here seven zones have been formed
since the injury ; and the chamberlets of these, whilst produced conformably to those of the
uninjured margin a, a, present the most marked want of conformity to those of the fractured

GENUS ORBITOLITES. 119

margin, which, nevertheless, they completely surround. A careful examination oi this
specimen, indeed, seems to me to leave little room for doubt, that the growth of the inner-
most or what I may call the rcparatirr zone of chamberlets took place, not from the broken
edge, but from the margin of the unbroken ; just as, to use a professional simile, an ulcerated
surface " skins-over" by an extension of the integument from its edges, not by the direct
formation of skin upon the granulation-surface itself All the six rows subsequently pro-
duced are conformable to each other and to the first or reparative row, from which they
have obviously extended themselves after the normal manner. It is observable, however,
that the breadth of these rows varies in different parts, being least where they invest the
projecting portions of the fractured edge, and greatest where they sink into its hollows.
And thus it comes to pass that the irregularities left in the shape of the disk, by the loss of
a large part of its substance, are gradually compensated, so as to restore it to a form much
more nearly corresponding to its typical symmetry. It is interesting to find evidence in
fossil specimens, that the same kind of reparation has taken place. Among the Orbitolites
which I have examined from the Calcaire grassier of Paris, is a disk of which a large part had
obviously been lost by fracture, but of which the original symmetry had been in great degree
restored by a similar outgrowth from the zones formed from the uninjured margin, along
the fractured edge. — In the specimen represented in fig. 27, in which but a very small frag-
ment appears to have served as the nucleus for a new disk, the tendency to the reproduction
of the typical form, by the compensative reparation just described, is still more curiously
marked. This specimen also presents the very unusual feature, that the new growth has
taken place from the inner margin of the original fragment {a, a), and not from its outer or
growing margin, as in the case previously noticed. Having carefully examined it in various
modes, I cannot entertain the slightest doubt that such has been the case ; for the chamber-
lets of the first new zone, as well as those of all the zones subsequently produced, are so
manifestly conformable to those of the thinner and older portion of the fragment, and are so
unconformable to those of the thicker and newer margin, that it seems obvious that the
sarcode must have extended itself from the former part, along the fractured edge on each
side, and have then enveloped the margin which had been left entire. This may have more
readily taken place in the present instance, because at the part a, a, the fracture seems to
have followed the course of one of the zones, instead of passing (as at the sides of this
fragment, and as in the instance previously cited) in such a direction as to cut the zones trans-
versely. — Again, I have met with several specimens, in which the central portion of the disk
having been broken-out, a growth of new zones seems to have taken place from without
inwards, so as to fill up the void space thus left ; the included portion being evidently as
unconformable to that which surrounds it as in the preceding case, and a void remaining
unfilled, the shape of one part of which clearly indicates that it occupies the site of the
original centre ; — so as to render the conclusion almost inevitable that the included portion,
and not the peripheral, must be the after-growth.

176. This series of abnormal phenomena, then, not only confirms the conclusion that
seemed fairly deducible from our previous examination of the normal mode of growth, with
regard to the independent endowments of the component segments of the sarcode-body of
Orbitolites, but also affords some additional information of much interest. For we see, in

120 FAMILY MILIOLIDA.

the first place, that there is no relation of necessary dependence between the several portions
of the disk ; since not only can the greater part of the peripheral portion be lost without
any diminution in the growing power of that which is left, but even a fragment of the peri-
pheral portion, altogether detached from the centre, can not only maintain its vitahty, but
become the centre of a new disk. Secondly, the growth of the sarcode and the addition of
new parts may take place not merely in the peripheral direction from the normal outer margin,
but also in the direction of the centre, provided that a free edge be exposed at the inner
margin of any zone. Thirdly, the reparative iiisus seems always to tend towards the pro-
duction of a disk whose shape shall approach the circular, whatever may be the form of the
fragment which serves as its foundation ; thus showing that, notwithstanding the repetition
and independence of the separate parts of these organisms, each cluster, whether large or
small, is an integer, having an archetypal symmetry to which it tends to conform, — strongly
reminding us of the phenomena of crystallization. And fourthly, the plan by which this
recurrence to the discoidal form is provided for, seems partly to consist in the limitation of
the new growth to the natural margins of the zones ; no such growth taking place from the
edge of a fracture which has crossed the zones transversely, although it may proceed from
the remains of a zone which has been broken off by a fracture that partly follows its course.

177. Varieties. — We have already seen that diversities both m \\\e diameter awA in the
thickness of the disk arise directly from the degree in which the animal substance (whereon
the skeleton is modelled) has extended itself either horizontally or vertically, so as to multiply
either the number of concentric rings, or tlie length of the columnar segments of which each
ring consists. This, however, is not the only source of variation in size ; for a most extra-
ordinary diversity presents itself in the dimensions of the individual components by whose
repetition the entire disk is made up. It is in the " primitive disk " that I find this diversity
most strongly marked, the central area of one specimen in my possession being about
twenty-eight times that of another, and every intermediate gradation being presented by other
specimens. There is not by any means the same amount of difference between the dimen-
sions of the ordinary segments which form the concentric annuli ; nevertheless, these also
exhibit marked diversities in size in different specimens (the largest chamberlets being usually
found to spring from the largest primordial chambers, and vice versa), and the individual
cells of the very same disk being occasionally found to differ no less widely amongst each
other. Similar differences present themselves in the vertical height of individual chamber-
lets ; as is of course best seen in the Simple type of Orbitulites, in which the augmentation
in the thickness of the disk is produced merely by the elongation of the columnar segments.
I possess a series of vertical sections of different individuals, in which the same gradual
transition is seen from the thinnest to the thickest, as I have just stated to exist in regard
to superficial area ; and which also proves that the relative thickness of the central and of
the peripheral portions is equally liable to variation. — It seems obvious, from the foregoing
considerations, that neither the absolute nor the relative dimensions of the individual parts
of these composite fabrics can, any more than the dimensions of the entire disks, be taken
as affording valid characters for the discriminatiop of species ; and that such a wide range
of variation exists among individuals, as would, if the extreme cases alone were known, seem
fully to justify their separation under distinct specific designations.

GENUS ORBITOLITES. 121

178. The appearances presented on minute observation by the surface-marUngs of Orhi-
tolifes, which indicate the form and arrangement of its contained chamberlets, are so far from
being uniform, that to any one whose eye had not become familiarised with their variety by
the examination of a considerable number of specimens, they would become sources of great
perplexity. We have already seen that the subdivisions of the annuli visible externally
present two very distinct forms, the rounded or oval (Plate IX, fig. 1), and the rectangular
(Plate IX, figs. 7, 9) ; the first of these being specially characteristic of that Simpler type of
structure in which there is only a single layer of cells, but not being confined to it ; whilst
the second is peculiar to the Complex type, in which there are two superficial layers distinct
from the intermediate stratum. Now the occasional co-existence of both these plans of struc-
ture in a single individual (t 172) sufficiently proves that the diversity of the surface
markings to which they respectively give rise, cannot be regarded as a basis for specific
distinction ; and when these extremes of diversity are kept in view, it must be felt to be
highly improbable that any modifications of either form should possess greater importance
That such modifications are mere individual varieties, is further evidenced by their gradational
character, and by the fact that two or more of them may present themselves in the same
disk. In describing them, I shall limit myself to an account of those more remarkable and
frequently-recurring varieties, which will serve, I think, as a key to any others that are
likely to be met with. — Although each surface, in either of the two principal types, ordi-
narily shows a division into concentric zones, which are again transversely subdivided so as
to mark the separation of the chaniberlets, yet sometimes the concentric zones are alone
visible, and no transverse subdivision is indicated, save by the alternation of hghts and
shadows proceeding from a like alternation of solid substance and of hollow spaces beneath.
This predominance of the concentric divisions, which gives a very distinctive aspect to the
disks that exhibit it, is usually most apparent in individuals whose vertical section exhibits
two planes of cells ; and it has seemed to me to depend on an unusual freedom between the
lateral communications, which I have noticed in certain individuals thus formed, so that the
animal portion of each zone might be described as an annulus of sarcode, merely constricted
at intervals. This peculiarly cyclical aspect of the surface may pass into either of the
principal types previously noticed ; the concentric zones sometimes breaking up (so to speak)
into bands of rounded chamberlets with slightly convex roofs ; whilst in other instances they
are subdivided by very definite transverse lines into cells of remarkable squareness, which
still retain the original flatness of their surfaces. — On the other hand, the appearance of
concentric division is sometimes almost entirely wanting ; the surface of the disk exhibiting
excentric circular markings, which resemble those of an engine-turned watch-case, and the
boundaries of the cells being formed by the intersection of these with each other. This
aspect, which seems due to an unusual freedom in the oblique communications between the
cells in each zone and those alternating with them in the contiguous zones on either side,
insensibly passes into the ordinary type ; and it is not uncommon to meet with disks, espe-
cially fossil, which exhibit in one part the engine-turned aspect, and in another that of
concentric zones transversely subdivided. Indeed I have sometimes found that the very
same disk might be made to present either of these aspects, according to the manner in
which the light is made to impinge upon it and is reflected from it. — Although the rounded
or oval form of the superficial divisions is specially characteristic of the Simple type of

16

122 FAMILY MILIOLIDA.

Orbitolites, yet it is by no means restricted to this ; being frequently met with in the thicker
disks of the more Complex type, and being almost constant in the fossil forms that abound
in the early Tertiaries. Its occurrence, however, may always (I believe) be considered as
indicating an incomplete separation between the superficial segments and the columnar seg-
ments of the intermediate stratum (f[ 1 73) ; so that the former present the shape of the latter,
in place of that which properly characterises them. The shape of the chamberlet is
sometimes marked out in unusual strength by the convexity of its roof or cover ; and this
feature is often so pronounced in the large fossil Orbitolites of the Paris basin, as to become
visible to the naked eye. A veiy marked diversity in its degree, however, as w^ell as in the
size of the cells, is often to be noticed in contiguous zones ; whence it is obvious that the
convexity is a mere accidental variation, and is a character of no value whatever as regards
the differentiation of species. The relation of the rounded to the square or rectangular
charnberlets is made evident by the occurrence of intermediate Unks of transition. — The
foregoing considerations seem to render it obvious, that diversities in the form of the super-
ficial chamberlets do not afford any ground whatever for the estabHshment of a corresponding
multiplicity of specific types, but that they must rank as individual variations to which there
is scarcely any definite limit.

179. Besides those regular markings of the surface which correspond to the division
of the interior into chamberlets, a peculiar aspect is frequently given to it by extraneous
calcareous deposits, which are sometimes irregular, but which occasionally present an
approach to radial symmetry. It is worthy of note that these deposits present themselves far
more frequently, and also in a far more characteristic manner, in the Orbitolites of the
Philippine Seas, than in those of the Australian or of any other provinces ; and this circum-
stance seems to render it probable that the outgrowth is directly due to the influence of
some external condition, probably an excess in the proportion of carbonate of lime in the
w'aters inhabited by these particular specimens.

180. Although the cyclical Mode of Growth, w-hen once established, is subsequently
maintained with great regularity, and although in what may be considered the typical form
it commences from the " primitive disk " itself, yet there are numerous instances in which
the typical regularity is more or less widely departed from, so that the early increase seems
to take place after an altogether different plan. The most marked antithesis to that regu-
larly concentric type of growth, in which a complete annulus of chamberlets immediately
surrounds the primitive disk (see Fig. XXIV, •[[ 157), is presented by those forms in which
the circumambient segment has only given origin to new segments at its extremity ; these
in their turn bud forth others, which extend and multiply themselves laterally as well as in
advance ; and thus a kind of spiral is produced, which opens out very rapidly, the lateral
portions of its mouth tending to grow round and embrace the primitive disk. An example
of this kind, in which as many as twenty-two zones (counting the primordial segment as the
first) succeed one another before the first complete annulus is formed, is shown in Plate IX,
fig. 5. Another example of the like abnormality, taken from a specimen in which the " primi-
tive disk" had a remarkably Milioline aspect, is shown in Plate IV, fig. 21. Now if these
two plans of growth — the one cj/clical from the beginning, the other cyclical only after having

GENUS ORBITOLITES. 123

been at first spiral — were constantly presented in well-marked contrast with each other,
there would be good ground for considering them, as Prof. Williamson has done (cviii),
to be characteristic of distinct specific types. But this idea cannot be sustained w'hen a
large number of individuals are examined and compared. For it then becomes apparent
that the number of cases in which the primitive disk is surrounded on all sides by the same
number of zones, indicating that the concentric mode of growth has prevailed from the
first, are very few ; but that in by far the larger proportion of specimens there is a slight
excentricity of the primitive disk, witli a larger number of zones on one side than on the
other, as in Plate IX, fig. 3 ; indicating that the first-formed zones have been incomplete
circles, owing to a restriction of the gemmation of the circumambient segment to one part of
its periphery. This is shown extremely well by decalcified specimens of the animal, scarcely
any two of which, in fact, precisely resemble one another as to the mode in which the first
zone originates in the circumambient. Thus in the specimen represented in Plate IV, fig. 14,
of which the primitive mass is represented on a larger scale in fig. 20, the circumambient
segment gives off only three peduncles, at the end most remote from its connexion with the
primordial segment ; and the first zone of segments is far from being entire, the cyclical type
not being completely attained until two or three successive additions have been made. In
fig. 1 9 ei^ht peduncles are seen to be given off from the circumambient segment, and from the
half-zone which they form an entire circle is next produced ; thus affording a remarkable con-
firmation to the idea I have already suggested (^ 1 75), as to the capacity of a portion of a zone
to give origin to a complete annulus, by the lateral extension of its bands of sarcode. In
fig. 18 the circumambient segment gives off eleven peduncles on one side, and there are
indications of iliree or four on the other. In fig. 17 the peduncles come forth from a still
larger proportion of the periphery of the primitive mass ; the zone which first surrounds it,
however, is still incomplete in some parts, though the succeeding zone forms an entire circle.
In fig. 15 we see peduncles coming off from various parts of the circumambient .segment, in
which (as in the specimens represented in figs. 16, 17, 18) there is a partial separation of
a secondary segment b' . Finally, in the specimen represented in fig. 1 6, which is almost the
exact counterpart of the disk represented in Plate IX, fig. 4, and diagrammatized in Fig. XXIV,
the peduncles come off from the entire circumference of the circumambient segment, and the
annular zones of segments are complete from the first. The greater the limitation of the
power of gemmation to one side of the nucleus, and the larger the number of incomplete zones,
the more will the early plan of growth approximate to the spiral type, such as is represented
in Plate IX, figs. 3, 5. — It is obvious that the existence of such intermediate gradations
breaks down that barrier between the extreme forms, which Prof. Williamson had proposed
to erect ; and shows that in this, as in many other particulars, differential characters which
at first sight appeared to be perfectly satisfactory, lose all their force when carefully traced
through a sufficiently extended series of specimens.

181. Monstrosities. — Besides those departures from the normal type of growth which
have been described as variations or irregularities, there are certain others of rarer occurrence,
which can only be regarded as " monstrosities by excess ;" consisting in the production of
one or more incomplete secondary disks by outgrowth from the first. Thus in one specimen
in my possession the secondary disk forms a half-circle B D, of about the same diameter with

B

124 FAMILY MILIOLIDA.

the primary a c, and is superposed vertically upon the latter, the plane of junction passing
i> through its centre. In other specimens the secondary disk is relatively

smaller, extending only from the centre to the margin of the primary, but

"^ s still meeting it nearly at right angles. — In another specimen I have met

with, it would seem impossible to say which is the primary and which the secondary disk ;

and it might be more correct to describe the entire structure as consisting of a single half-

'C disk A B and of two half-disks b c and b d, meeting each other at an acute
angle c b u, neither of them being in the same plane with the single half-
disk, but both of them meeting it at similarly obtuse angles A b c and a b D.
In another case there rises from the surface of the disk a triradiate crest, formed by three
vertical plates meeting one another at nearly equal angles, but all of them neai'ly perpen-
dicular to the plane on which they rest. It is a very remarkable feature in this specimen,
however, that the line in which the three vertical planes meet is traceable at its base to the
centre of the horizontal disk ; so that they all bear the same relation to the primitive disk as
does the single outgrowth in the instances previously cited. Hence we may attribute all
such monstrosities (of which I possess a remarkable collection) to an excess of productive
power in the sarcode of the primordial segment, which has put forth its first extension, not
merely in the horizontal, but also in the perpendicular direction ; the whole subsequent
development of these outgrowths taking place after the normal plan, from the foundation
thus laid. I have occasionally met with instances, however, in which a vertical plate rises
from the peripheral portion of the disk, at a distance from the primordial chamber. — It is
interesting to remark that the presence of such outgrowths as those now described is far
more frequent in certain localities than it is in others. Among some hundreds of specimens
which I have examined from the coast of Australia, I have only met with five or six ; among
those yielded abundantly by the sand of the shore at Suez, such monstrosities are far more
frequent, and the excess more pronounced ; but in a small collection which I have inspected
from the Mgean Sea, the monstrosities of this kind were so numerous, that I think I am
scarcely vsTong in asserting that one specimen out of every three or four presented some
excess.* Among the fossil Orbitolites of the Paris basin, the presence of a completely
semicircular vertical plate is not at all uncommon.

182. Essential Characters of Orbitolites, and its Relations to other Types. — If, now, we
seek to determine the essential characters of Orbitolites, we find them to lie in the presence
of a series of annuli of sareode (and of corresponding galleries in the shelly disk) arranged
concentrically round a "primitive disk," which resembles a young Miliola ; each zone in the
simpler type containing but a single annulus, so constricted at intervals as to form a series of
somewhat columnar segments, which occupy the chamberlets of the shelly disk and are con-
nected with each other by stolons of sarcode ; whilst in the more complex type each zone

* This is by no means a solitary case of tlie prevalence of monstrosities in particular localities.
The collection of Mr. Bean, of Scarborough, contains a number of curiously distorted specimens of
the common Planorbis marftnatus, which have all been collected in one brook. Their peculiarities are
by no means repetitions of each other ; and I am disposed, therefore, to regard tliera rather as
resulting from the influence of external conditions, than as accidental varieties hereditarily propagated.

GENUS ORBITOLITES. 125

contains two such annuli, including between them a portion of its series of columnar segments,
so as to constitute an intermediate stratum, distinct from the snpcrfcial portions. In either
case, the segments of successive zones freely communicate with each other by radiating
peduncles of sarcode (also leaving jorwwyes in the shelly disk), whose normal direction is such
as to connect each segment with the two segments that alternate with it in each of the
adjacent zones. — The extreme freedom with which all the cavities of the shell mutually
communicate is a very marked feature in the structure of this type, as in that of Ortjiculina,
Alveotina, and Fab id aria ; and shows that the several parts of their animal bodies are far
more closely connected into one whole, than they are in those Foraminifera with perforated
shells which they most resemble in general plan of conformation. — The addition of
new zones, each similar to the last, is a simple matter of rjrowlli ; but the passage from
the Simpler to the more Complex plan marks an advance in devetopment ; and this
advance essentially consists (here as elsewhere) in a progressive differentiation of parts.
When, with the vertical extension of the columnar segments, the annular canal subdivides
itself into two, the communications between the successive zones no longer come-off, as
before, from the annular canal, but from the intermediate portions of the columnar cells ;
and instead of the two diverging passages from each cell being in the same plane, they lie in
different planes, alternating with each other vertically. Up to this point, we observe little
else than a multiplication of parts vertically, as well as horizontally, and a separation of con-
nexions that were previously confluent. But in the highest stage of development we find a
marked alteration in plan ; for those portions of the columnar segments, which lie between
the two annular canals of each zone and the two surfaces of the disk, become completely
differentiated from the portions that occupy the intermediate stratum, so as to form a peculiar
set of superficial chamberlets ; and these are so equally connected with two zones, as to make
it impossible to say that they belong specially to either. — Now we have seen that development
may be checked, while r/rowtlL continues, at any period of its progress ; so that we find
Orbitolites growing to a considerable size upon the very simplest plan, others still larger
formed upon the duplex plan, the largest yet known (fossihzed in the Paris basin) developed
upon the multiple plan without separation of the superficial chamberlets, while the most
complete, in regard alike to mvdtiplication and to differentiation of parts, are only found
among the disks at present existing; audit is interesting to observe that some of these
present this highest grade of development, while as yet of comparatively minute size.
There is scarcely any other type of Animal structure, in which so wide a range of develop-
mental variation normally exists. The lower classes of the Vegetable Kingdom, however,
especially the group of Fungi, afford abundant examples of it.*

183. The relation of Orbitolites to Orbiculina is of the most intimate kind. As already
mentioned (•[[143), it would not be possible to distinguish with certainty a fragment of the peri-
pheral portion of the former from a corresponding fragment of the cychcal type of the latter ;
though it is curious to observe that, whilst the differentiation of the superficial from the inter-
mediate strata is most complete in the Orbiculince of the early Tertiaries, it is least complete
in the Orbitolites of the same epoch ; and conversely, whilst it is least complete in the Orbiculina

* For a more detailed examination of the reputed species of Orbitolites, see xiii, p. 224.

126 FAMILY MILIOLIDA.

of the present time, it is most complete in the Orbitolites of our Southern Ocean. These
two types are at once distinguishable from each other, however, by a comparison of the centres
of their respective disks ; for not merely does OrhicuUna invariably commence on the spiral
plan, but it invariably persists in this until the spire has made three or four turns, of which
each invests the preceding, so as to augment the thickness of the centre, and to cause this to
project as a rounded knob above the plane of the peripheral portion of the spire or disk. In
Orbitolites, on the other hand, the cyclical mode of growth seems characteristic of the type ;
for even when the early growth follows a spiral arrangement, this seems simply to result from
a defective power of gemmation in the " primitive mass " of sarcode, and the spire never
proceeds beyond a single turn, or encroaches on the surface of the primitive disk, but from
the iirst shows a tendency to pass into the cyclical form.

184. The relation of Orbitolites to Tinoporus (the Orbitolina of D'Orbigny), to Orbitoides,
and to Cycloclypeus, is one of mere similarity in mode of growth, and consequently of analogy
only ; their essential characters being such as to remove them most widely from it. For as
Orbitolites is the cyclical type of the Milioline series, so shall we see that Tinoporus stands in
the like relation to the Rotaline, and Cycloclypem to the Operculine, whilst Orbiloides seems
to be a connecting link between the two latter.

185. Geographical Distribution. — This type, like OrbicuHna, is pretty generally diffused
along the shores of the warmer seas ; but it is interesting to observe that it is most abundant
where Orbiculina is comparatively rare, and vice versa. Thus, it is more commonly met with
in the Australian and Polynesian seas than in the West Indian or Philippine, and is peculiarly
abundant in the Red Sea (the shell-sand of Suez yielding it in extraordinary copiousness),
though not there attaining any large size or high development, whilst it seems to die out in
the Mediterranean, the specimens gathered on its shores being all of stunted growth. Its
largest size and highest development at the present time are attained in the Polynesian seas,
especially on the sides of Coral-reefs, where the disks that have become detached from the
sea-weeds to which they are usually attached, often accumulate to an enormous extent.

186. Geological Distribution. — The early part of the Tertiary period appears to have
been unusually rich in Foraminifera of the largest size. The C'alcaire Grossier of the Paris
basin, and corresponding formations in the south of Europe, contain enormous numbers of
Orbitolites, which often attain a diameter of 8- 1 Oths of an inch ; and the Limestones of the north-
west of India, which in some parts are rich in Orbicidina and Qrbitoides, are elsewhere almost
entirely composed of an equally large variety of Orbitolites, which Mr. Carter (xix) has
described under the name of Cycloliua, supposing it (from the peculiarly cyclical aspect of its
surface, 1178) to belong to the genus so named by D'Orbigny, which seems, however, to
have been really founded on a varietal form of Tinoporus. The true Orbitolites first makes
its appearance in the rich Polyzoic deposits of the shallow-water Maestricht chalk ; and it
has probably continued to inhabit the ocean waters, from the time when it first accumulated
so as to form an important constituent of the Eocene Limestones, down to the present epoch.
Whenever the Coral islands at present submerged shall in their turn undergo elevation, a new
series of Orbitolite-limestones, now in progress of formation, will probably be brought to light.

GENUS DACTYLOPORA. 127

Genus XI — Dactylopora (Plate X).

187. History. — The most singular varieties of opinion have existed as to the true cha-
racter of the fossil organisms on which the genus Dactylopora was founded by Lamarck (lx).
They had been previously noticed by Bosc, and had been referred by him to the genus
Heteporitcs, belonging to the group then regarded as Zoophytes, but now ranked as Polyzoan
Mollusca ; and in this allocation he was followed by Laraouroux. In separating them gene-
rically from Betcpora, Lamarck still associated them in the same group of supposed Zoophytes ;
his genus was adopted by Blainville and Defrance (vii), who assigned the like place to it ;
and it was accepted by many subsequent palaeontologists, as Goldfuss, Michelin, and Bronn,
without any question as to its character. By Blainville and Defrance, moreover, another genus,
PoJyfrype, was erected upon a mere variety of the same type ; and this also has been accepted
as a zoophytic form nearly allied to the preceding. In 1852, however, Bactytopora was included
among the Foraminifera by ]M. D'Orbigny (lxxiv) ; who showed, notwithstanding, by the place
he assigned to it, a misapprehension of its real nature scarcely less complete than that under
which his predecessors had lain ; for he ranks it in his Order Monosfeyues, next to the unilo-
cular Ovulites, and says of it : — " C'est une Ovulite egalement percee des deux bouts, pourvue
des larges pores places par lignestransverses." How utterly erroneous is this description will
appear from the details to be presently given ; yet M. D'Orbigny's authority has given it currency
enough to cause it to be accepted by such intelligent palaeontologists as Pictetand Bronn, who,
in the latest editions of their respective systematic treatises, have transferred Dactylopora to the
place indicated by him, not without the expression of a doubt, however, on the part of the last-
named author (x, 'Uebersicht,' p. 25), whether its true place is not among the FistulidcB, in alliance
with Synapta and Ilolotlwria, — a suggestion that indicates a perversion of ideas on the subject,
for which it is not easy to account. The complex structure of the organism in question was
first described, and the interpretation of that structure on the basis of an extended comparison
with simpler forms was first given, by Messrs. Parker and Rupert Jones (lxxix) in so unob-
trusive a manner as scarcely to challenge the attention which their investigations deserve ; and
I gladly avail myself of the opportunity which the present publication affords to give a fuller
account, with the requisite illustrations, of this remarkable type, the elucidation of which
seems to me not unlikely to lead to a reconsideration of the place assigned to many other
organisms at present ranked among Zoophytes or Polyzoa. This account will be chiefly based
on the descriptions already given (loc. cit.) by those excellent observers ; but it will depart
from these upon several points, as to which the further investigations which we have jointly
prosecuted have led to a modification of their original conclusions. The illustrations in Plate X
are carefully drawn, by Mr. G. West, from the beautiful series of specimens with which they
have furnished me, and which they have kindly allowed me to treat in any manner that I
thought desirable for the elucidation of their structure.

188. External Characters and Internal Structure. — The t3'pe we have now to investigate
is one which, like the three preceding, exhibits itself under such a variety of modifications of
form, and so many dissimilar phases of development, that only by a careful and extended

128 FAMILY MILIOLIDA.

comparison can the mutual relations of these be discovered ; and it will be desirable, instead of
commencing with the complex organism on which the genus was originally established, to
examine in the first instance those simpler or more elementary forms which afford the clue to
the interpretation of its character. For each of the principal modifications I am about to
describe, I shall adopt the distinctive name assigned to it by Messrs. Parker and Rupert Jones ;
but these names are to be understood as used merely for the sake of convenient identification,
and not as intended to indicate a definite boundary between the forms the}^ respectively desig-
nate, — no such boundary having, in our opinion, a real existence.

189. In the East Indian and other tropical seas, generally adherent to the surface of
large, foliated, bivalve shells, such as Chama or Hippopus, but occasionally free in shell-sands,
the simple pupoid forms represented in Plate X, figs. 1 — 7, are not uncommon. Each of these
is composed of a linearly-arranged series of chambers entirely disconnected from each other ;
the external walls of these chambers and their dividing septa are very thick, and are
composed of porcellanous shell-substance exactly resembling that of the higher types of
Foraminifera with which we have been last engaged ; and their surface sometimes exhibits
minute pits, resembling those which we have seen to be common on the exterior of many of
the porcellanous series. Although the succession of these chambers is sometimes almost
rectilinear, it is generally more or less curved ; and the curvature is sometimes so great
that the series forms a half ring. Every chamber opens separately by a single large pore on
the middle of the concave side ; and this pore is surrounded, as in Pe/ieroplis, Orhitolites, &c.,
by a prominent annulus of shell, which is sometimes so thick and large as to form a nipple-
shaped protuberance. The number of chambers is extremely variable, and is obviously depen-
dent upon successional growth. Although specimens are occasionally met with in which the
surface is smooth or nearly so, it much more commonly presents a strongly marked alternation
of ridges and furrows (figs. 3, 7), the former corresponding with the interseptal spaces, and the
latter with the septa ; there are instances, however, in which the interseptal spaces are depressed,
as in fig. 8, instead of being elevated. It now and then happens that the chambers are piled one
on the other, so as to form part of a double series (fig. 6). The length of any series will, of
course, depend upon the number of chambers which it contains ; the breadth of these bodies
usually varies between '007 and 012 incli. Tlie simple structure of this organism is diagram-
matically represented, as shown by horizontal and vertical sections, in Fig. XXV. Its mode of

growth would be not a little perplexing, if we did not bear
Fig. XXV. in mind what has been already stated as to the extension of

the sarcode-bod}' over the exterior of the shells of Forami-
nifera (^ 33), and the formation of new envelopes by portions
of that body protruded from the aperture (^ 31). It has

been shown to be probable, in the case both of Orhitolites
Diagrammatic Sections of Dactylopora -, ^i t •• •/• ii-ii\i

m,«:-A, horizontal; e, vertical. ^nd AheoJina, that (at certam tmies, if not habitually) the

pseudopodial extensions from the separate pores coalesce with
each other on the exterior of the aperture ; and there is no more difficulty in understanding
how, from such a coalesced stolon of sarcode, a new chamber may be added to either extre-
mity of the linear series, or may be built (so to speak) as part of a new storey above it, than
there is in accounting for the formation of such a chamber in direct continuity with the aper-

GENUS DACTYLOPORA.

129

ture of the preceding. We shall presently see in the more complex forms of Bactylopora a
very marked indication that such a coalescence really takes place ; the apertures of the
principal chambers being received into a gallery that obviously lodged a stolon by which the
isolated segments are brought into mutual connection. — The type now described, which
presents itself in some of the French Tertiaries under a form (see figs. 4, 8) precisely identical
with the recent, is distinguished as D. eruca.

Fig. XXVI.

190. It is obvious that the continued growth of such bodies along a circular curve would
ultimately complete them into rings ; but it does not appear that such an elongation of the
pupoid form of Bactylopora ever takes place, as would be required to complete the large
circle which their moderate curvature would generate. In the " calcaire grossier " of
Grignon and other Tertiary deposits, however, the pupoid forms are accompanied by complete
annular disks (figs. 10 — 14), having a structure in every essential respect similar to theirs,
and varying in diameter from -025 to -035 inch. Each of these rings is composed of a series
of flask-shaped chambers, usually from ten to twenty-four in number, regularly packed side
by side ; the chambers being surrounded by thick walls and
separated from each other by thick, imperforate septa, as is
shown diagrammaticallyin Fig. XXVI, a. Each chamber opens
into the central cavity of the annulus by a single aperture in
the centre of a mamillary protuberance ; this protuberance,
however, is usually nearer to one surface of the disk than
it is to the other (Fig. XXVI, b) ; and it is not always seated
on the internal margin of the ring, but is sometimes a little
removed from it on the surface of the disk, and then points,
not directly, but somewhat obliquely inwards, as shown in
figs. 11, 14. The surface of the annular disks exhibits the
same varieties as that of the pupoid forms, being sometimes
uniform, but more commonly presenting an alternation of
radiating elevations and furrows, the furrows corresponding
to the septa, and the elevations to the intervening spaces
that cover-in the chambers beneath. The number of the
elevations and of the intervening furrows, however, is
usually much greater in these annular forms than that of the chambers ; for the primary
elevation is often itself divided into two ridges by a secondary furrow, especially towards the
outer margin of the annulus ; and thus we have a series of sharply defined radiating ridges
(fig. 13) resembling the teeth of a flat wheel, the furrows between which, however, do not
all extend to the inner margin of the annulus, which may be divided only by those that
correspond to the septa. This ridge-and-furrow arrangement is far more strongly marked
in some instances than it is in others ; a gradational variety being obvious, on the comparison
of a sufficient series of specimens, between the smoothest and flattest of these annular disks
and those whose surface is most unequal. In some instances, moreover, the ridges are con-
tinued along the outer margin of the annulus, so as to give it the appearance of a wheel
toothed at its edges ; and it is curious that this dentated margin is sometimes most strongly
exhibited by disks whose surfaces are the flattest, as is shown in fig. 19. There is a

17

Diagrammatic sections of Bactylopora
annulus : — a, horizontal ; b, vertical.

130 FAMILY MILIOLIDA.

considerable variety, too, in regard to the proportion whicli tlie central space bears to the
breadth of the annulus ; the inner circle being for the most part relatively smaller in the
flattest annuli, and increasing in diameter as the annulus itself swells out and diminishes in
breadth. It is a remarkable feature in this type, which may be distinguished as D. annulus,
that the annulus is usually divided with great regularity into chambers of equal size ; a
regularity 7or which it is difficult to account on the supposition that the entire ring
has been developed by the successive growth of independent chambers. After a careful
examination of numerous specimens, I have only met with one which gives any distinct
indication of a line of junction, such as might be expected to result from the meeting
of the two ends of an imperfect ring completed by the successional addition of new
chambers. And it may therefore be fairly questioned whether the uniform annulus, which
is certainly the normal type, did not originate in a radiating outgrowth of segments from one
large primordial mass of sarcode occupying its centre, in the same manner as the first
annulus of chamberlets in the typical Orhitolites (^ 161) is formed around the primitive disk;
the space at first occupied by the primordial segment being not covered-in by shelly w^alls,
and being perhaps vacated in these annular forms so soon as the surrounding ring of
chambers has been consolidated. We shall hereafter see reason to believe that in the more
complex type of Dadijlopora the central cavity continues to be occupied b)" the sarcode-body
through life, and that it is in this portion that all new annuli have their origin (f 197).

191. In each of the two forms now described a curious variety is occasionally met
with, resulting from what may be termed a " wild "' growth of the segments (such as we shall
frequently encounter in certain forms of the vitreous series), which tends to convert the
closely set, flask-shaped chambers into elongated, divaricating tubes. This is most strongly
marked in the pupoid type, the chambers of which occasionally undergo such an elongation
as to be converted into cylinders (fig. 16) so closely resembling the cells of Ti/biiUpora or
Celh'pora, that, if detached from each other, they might easily be mistaken for fragments of
those Polyzoa ; and, in fact, the determination of this form as a variety of Bactyhpora, under
the designation B. dic/itaia, chiefly rests on its evident relationship to that to be next described.
No specimen has yet been found sufficiently perfect to exhibit the unbroken terminations of
the cells ; but there can be no reasonable doubt that they are closed at their diverging
F XWII extremities (as shown diagrammatically in Fig. XXVII),

hke those of the forms to which they are related. — A

similar tendency occasionally shows itself in a less

marked degree in the annular type (fig. 15); giving

rise to the form which has been described and figured

by Michelin ('Icon. Zooph.,' p. 177, pi. xlvi, fig. 27),

under the name of Cli/peina mar^inoporella, as a member

of the family TuhuUporida. The chambers here also

are elongated and subcyhndrical ; but they remain in

Diagrammatic seetior7z)../^/o^.m^,>,-^«/a,- adhesion to each other laterally, so as to lie obliquely

—A, horizontal; b, vertical; 1, 1, line of to the axis of the ring, and to form a sort of inverted

^™'"'^'^' . funnel, as is shown in the diagrammatic sections in

Fig. XXVIII. The pores represented by Michelin along the external margin have no real

GENUS DACTYLOPORA.

131

walls

Fig. XXVIII.

existence, being merely the result of the attrition of the most exposed part of the
of the chambers ; and the true apertures of the chambers are
seen along the inner margin of the annulus. It is convenient to
retain as the specific designation of tiiis organism the generic
name conferred upon it by Michelin ; so that we shall dis-
tinguish it as D. dypnna* — The resemblance which B. digitata
and B. dypeina bear to tubuliporous polyzoaries is much
strengthened by the deep pittings of their surface, which so
nearly present the aspect of the perforations common in the
shelly walls of the cells of Polyzoa, as to be readily mistaken for
them. It is to be borne in mind, however, that such deep
pittings are not infrequent among the porcellanous Foraminifera
(^ 111, 138) ; and we shall find similar, though shallower, pittings
presenting themselves in other forms of Bactyhjmra.

1 92. Returning now to the ordinary type qID. annulus, we have Diasiammatic sections of DacUj-
next to remark that it is not uncommon to meet with two or more fo^jora c(y;ja«a .— a, horizoutal ;
rings adherent to each other serially by their surfaces (fig. 9); e, venca.
when these surfaces are flat, there will be no spaces left between them ; but when raised into
ridges, the mutual adhesion of these ridges completes the intervening furrows into canals
(Fig. XXIX, a, a). These canals may or may not pass through the entire breadth of the annulus,
according as the furrows by the junction of which they are formed are primary (septal) or are
secondary (intermediate, % 190) ; and even the septal furrows do not always extend to the interior
of the annulus, so that there may be every kind of variety in the size and number of thesg /K»cfera/
interspaces. In what may be considered the typical form of this variety, which is designated
B. reticulata, the symmetrical piling of the rings one upon another forms a compact cylinder,
the exterior of which is marked at regular intervals by single rows of large pores closely approxi-
mated to each other (figs. 17 b, 1 8, c/ a'), and in the intervals between these by the marginal ridges
of the annuli. On the internal surface the annuli are less intimately connected with each other,
as their projecting ribs most commonly stop short of the internal margin of the ring ; and thus •
there is seen a deep grove or furrow (fig. 1 7 b, 5 h') at the junction of each pair, from the peri-
pheral margin of which the junctural interspaces diverge. The apertures (e) of the chambers
{d, d) seldom, if ever, lie in the median plane of the annulus, but are directed more or less
obliquely towards one of its surfaces, so as to appi'oach the furrow just mentioned ; and their
obliquity is sometimes so considerable that they discharge themselves into that furrow. — But
if the surfaces and margins of the rings should be nearly smooth, the pores formed by the
"junctural interspaces" will be very small and inconspicuous ; and when, as often happens,
these are filled up by fossilizing deposit, the composition of the column will only be indicated
externally by the constrictions which it exhibits at intervals. In other cases, again, the "junc-
tural interspaces'' are of extraordinary size.— It not unfrequently happens that the cavities
of the chambers are laid open by attrition (fig. 17 b, c' c')) at the parts of the surface [c, c)

* By Messrs. Parker and Rupert Jones the specific designation marginoporella was the one
employed ; but this is so obviously inappropriate as to render its retention undesirable.

132 FAMILY MILIOLIDA.

where their walls are thinnest ; and such specimens, worn down to the line 1, 1, in Fig. XXIX,

will present a series of large pits or openings between the rows of " junctural interspaces.'' This

seems to be the condition of the form described by Defrance (xxix, torn, xxv, p. 287), under

the name Larvaria reticidata ; and as there is here nothing

Fig. xxix. inappropriate or deceptive in the trivial name, we retain it

to distinguish the form of Badi/lopora now described. The

f'^i^' '5^rirK close relationship between this type and the preceding is

/ Ws>^\ T^^ ( evident.not merely from the general identity in the composition

ckSS^^ ^-"-"—iS^SS" of each annulus, but also from the circumstance that the

)C ^/f ?^°*^( average number of chambers which it contains is the same in

aSSiSI — ' W«s«wf -^- reticulata as it is in I), annulus, and that the average

Xf^y? ^^y diameter of the cylinder of the former is the same as that

\^^~J- — - L_!-^^ of the rings of the latter. There is, in fact, every gradation

between those disconnected rings, which are not unfrequently
Diaarrammatic vertical section of Z'fft'/y- r i i- i i it • ■ i ^i i <•

loporaretic^.lata:-a,a,a,a,\.^r.A^:x^\ found shghtly adherent m pairs, and the compact column of
interspaces; 1, ], line of attrition. which the original annulation is but very imperfectly indi-

cated on the surface. It is to be noticed in some of the most
compact specimens of this type (fig. 21) that the succession of the chambers in the adjacent
rings is not altogether regular, but that they in some degree alternate with each other, so as to
present a transition to the next variety ; and even when the annular divisions are well marked by
the rows of large "junctural interspaces,'' these divisions are sometimes considerably inflected.

193. A modification of this simple type sometimes presents itself, in which the chambers

are more than usually isolated from each other ; each being surrounded on all sides by its own

proper wall, and "being connected with the adjacent chambers by projections of that wall '

(Plate X, fig. 25) ; between these projections are left "junctural interspaces" ij), h), which are

sometimes passages of considerable size (fig. 28), and are sometimes narrowed to mere pores

(fig. 26, 27). The apertures {a, a) of the chambers are here uniformly central, and are seated

on nipple-shaped prominences (figs. 25, 26, 28). The external surface of the walls of the

•chambers, in well-preserved specimens, is roughened by an irregular sculpture (fig. 27) ; a

circumstance of interest with reference to the nature of the original surface in D. ci/Iinclracea.

The piling of these chambers one upon another is not, as in D. reticulata, in distinct annuli ;

for, although they usually form tolerably regul