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GALBRAITH & HAUGHTON'S SCIENTIFIC MANUALS.

Experimental and Natural Science Series.

MANUAL

OF THE

ANIMAL KINGDOM.

I.

PROTOZOA.

BT

PROFESSOR J. REAY GREENE.

NEW IMPRESSION.

LONDON:
LONGMANS, GREEN, AND CO.

1868.

MANUAL

OF THE

SUB-KINGDOM

PROTOZOA.

WITH A GENEBAt UfTEODrCTION OK

THE PEINCIPLES OP ZOOLOGY.

BY

JOSEPH REAY GREENE, B.A.

PROFESSOK OF NATURAL HISTORY IN THE QUEEN'S COLLEGE, CORK,

&c. &c.

NETW IMPRESSION.

LONDON:
LONGMANS, GREEN, AND CO.

1868.

LOITDON : PEI5TKD ET

8P0TXISW00DB AND CO., NKW-STEEET SQCAB^

AKS FABLIAMENI STB££I

^<^/* ^m^ <y^-'

PREFACE.

It has been the Author's aim to embody, in the
presect Manual, a succinct resume of what is
known concerning those humbler forms of animal
life which constitute the department of Protozoa :
and in so doing, he has, as much as possible,
sought to interpret the observations of others by
the light which he has gained from the results of
his own investigations.

A list of the more important memoirs on the
Protozoa has been appended to the general ac-
count of these animals, in the hope that it may
prove useful to those advanced students who may
be desirous of entering on their special study.

Titles are affixed to the numbered paragraphs,
both with a view to facilitate reference, and also
to guide the junior student in selecting those
branches of the subject, with which, on a first
perusal, it is most desirable that he should be
made familiar. It will be found, however, that

A 3

Vi PKEFACE.

the general plan of the work is independent of
these artificial divisions.

In treating of the classification of the Protozoa,
it will be seen that the expressions, class, order,
family, and genus, ai'e not here made use of. To
these terms a definite meaning is, or ought to be,
always attached, and it would, therefore, be pre-
mature to apply them to the subdivisions of the
Protozoa ; the natural groups into which this de-
partment is resolvable not having been yet deter-
mined with absolute certainty.

Since the present work is the first of a series
of similar treatises, on the several departments of
the Animal Kingdom, it has been deemed neces-
sary to prefix thereto a brief introduction on the
general principles of zoological science.

Queen's College, Coek,
Maj', 1859.

CONTENTS.

General Introduction

Page
- ix

CHAPTER I.

PROTOZOA.

1. General characters. — 2. Classification - - - i

CHAPTER 11.

RHIZOPODA.

I. T}'pe of the Group: Amoeba. — 2. Nature of Rhizopoda. —
3. Rhizopoda allied to Amoeba. — 4. Classification of Rhizo-
poda.— 5. Foraminifera. — 6. Classification of Foraminifera.
— 7. Unilocular Foraminifera. — 8. Polythalamia. — 9. Struc-
ture of the shell in Foraminifera. — 10. Technical terms. —
II. Distribution of Foraminifera in Space. — iz. Distribution
of Foraminifera in Time. — 13. Size of Rhizopoda. — 14,
Development of Rhizopoda - - - - - 3

CHAPTER in.

POLYCYSTINA.

X. Nature. — 2. Distribution - - - - - 28

A 4

39TG1

yiU CONTENTS.

CHAPTER IV.

SPONGID.E.

Page
I. Animal nature 2. Form and Size. — 3. Skeleton, — 4. Aqui-
ferous system. — 5. Reparative powers. — 6, Spicula. — 7.
Classification. — 8. Structure of Tethya. — 9. Development.
— 10, Distribution. — J I. Affinity to Foraminifera - - 30

CHAPTER V.

THALASSICOLLIB^.

I. External characters. — 2. Organisation. — 3. Acanthometrs - 44

CHAPTER VI.

GREGARIXID^.

I. Habit. — 2. Form and Stnictiire. — 3. Development. — 4. Clas-
sificaticm. — 5. Psorospermiae - - - - 49

CHAPTER VII.

INFUSORIA.

I. Nature of Infusoria. — 2. Example of the Group : Vorticella.
— 3. Classification. — 4. Size. — 5. Form and Structure. — 6.
Digestive apparatus. — 7. Contractile vesicle. — 8. Nucleus,
&c. — 9. Urticating organs. — 10. Locomotive organs. —
II. Development. — 12. Distribution. — 13. Noctiluca -53

Bibliography of the Protozoa - - - - 79

Questions on the Protozoa - - - - - 83

List of Illustrations - - - - - - 85

Index - - - - - - - - $6

GENERAL INTRODUCTION.

ON THE PRINCIPLES OF ZOOLOGY.

Biology is that branch of scientific inquiry which
undertakes to investigate the nature and relations
of living bodies. It is the object of this science,
by a careful study of the several beings of which
the organic world is composed, to ai-rive at a
knowledge of those general " laws " by which it is
governed.

Every living being may be regarded from two
points of view, which it is necessary to distinguish
clearly from one another. The first of these ex-
hibits to us living beings as possessing definite
forms, which, in most instances, are found to be
made up of a number of dissimilar parts or organs ;
while the second takes cognisance of the vital
actions ox functions which those organs perform.
That department of Biology which determines
the former is termed Morphology; that which
investigates the latter Physiology, Hence the

X INTRODUCTION.

nature of living beings is two-fold — Morpho-
logical and Physiological.

The relations of living beings may, in like
manner, be viewed under two distinct aspects,
namely :

1. Their relations to one another, i. e. their
mutual or subjective relations.

2. Their relations to the conditions in which
they are placed, i. e. their external or objective
relations.

We endeavour to express our appreciation of
the first kind of relations in our attempts to frame
a natural Classification; whilst our knowledge of
the second is involved in a statement of those
facts from which, it is hoped, we may be enabled
to deduce the laws of Distribution,

But what are the characters of living bemgs,
and how may they be distinguished from the
members of the inorganic world ? This question
presents itself for solution at the outset of our
inquiries, since it is desirable to determine the
limits of the region which we have undertaken to
explore.

To frame a definition of life, is, however, im-
possible, this agent being only known to us by its
effects.^ When the so-called vital principle is
associated with matter, as in a living body, we
invariably observe that it confers upon the latter
a tendency to pass through a series of changes.

INTEODUCTION. XI

Such changes are always definite and follow one
another in a determinate order. This is the most
general and characteristic feature of living beings,
since matter, of itself, if unacted on from without,
is incapable of undergoing any change.

Other peculiarities, of minor importance, dis-
tinguish living from inorganic bodies. Of these,
the principal have reference to external form,
internal structure, cheriiiical constitution, and
mode of increase.

1. External form. — The figure of living beings
is always more or less rounded, being bounded by
convex surfaces. That of inorganic bodies, on the
contrary, is either indefinite (amorphous), or, if
regular (crystalline), is, mth very few exceptions,
bounded by angles and right lines.

2. Internal structure. — The structure of a
mineral body, provided it be pure and unmixed
with any other substance, is altogether homo-
geneous, consisting throughout of an aggi'egation
of similar particles. Such a body, therefore, can-
not properly be said to possess any structure
whatsoever, whereas the body of a living being
usually consists of several parts, distinct from one
another, which, again, in their turn, are seen to
be composed of more minute constituents or tissues,
these last being yet again resolvable into certain
ultimate elementary components. Hence their
structure is said to be heterogeneous, and the ex-
pression organised bodies has come to be synony-

Xll INTRODUCTION.

mous with living beings. There are, however,
some organisms of exceedingly simple structm'e,
which offer apparent exceptions to the universality
of this distinction.

3. Chemical Constitution. — The body of every
living being is found to be composed of the essen-
tial elements, carbon, hydrogen, oxygen, and,
probably, also, nitrogen, to which other simple
substances may be superadded. No such uni-
formity can be predicated of the composition of
inorganic bodies.

4. Mode of increase. — The increment of inor-
ganic bodies is effected by the addition of similar
particles to their exterior, while that of living
beings is due to the assimilation of nutrient
matters received into the substance of their bodies.
To such a mode of increase, the term groivth is
more properly applied.

The organic world includes two great groups
of beings, plants and animals. These agree
with one another in the possession of the above-
mentioned characteristics, by which, as a whole,
they differ from inorganic bodies. They agree,
also, in their ultimate structural characters. They
have, moreover, a similar origin, since both alike
spring from germs, i.e. minute independent living
molecules, for the production of which parent
organisms are necessary. How then may they
be distinguished from one another ?

INTRODUCTION. XIU

The larger animals, especially sucli as are either
useful or dangerous to man, and with which,
therefore, most persons are familiar, differ so
much, in the adult condition, from the more con-
spicuous members of the vegetable kingdom, by-
reason of their powers of voluntary locomotion, as
also by the anatomical feature of possessing a
nervous system, that the present inquiry might
seem, at first sight, unnecessary and even ridicu-
lous. What resemblance is there, it might be
asked, between a bird and the tree on which it
perches, or a cow and the grass upon which it
feeds ?

But the scientific naturalist is acquainted with
numerous aquatic organisms, most (though not all)
of these being of minute size, whose true position
whether in the animal or vegetable kingdom has,
of late years, afforded matter for abundant contro-
versy. Many of these creatures, while presenting
affinities to undoubted plants, are nevertheless
capable of executing movements which have
been frequently compared to those of animals.
Besides, there are other living beings, fixed dur-
ing the entire period of their lives, whose animal
natm^e is not likely to be called in question. Fm^-
ther, several animal forms, universally recognised
by naturalists as such, exhibit no traces of a ner-
vous system.

The presence or absence of locomotive power, and
of a nervous system, will, therefore, in many cases,

Xiv INTRODUCTION.

be insufficient tests whereby to distinguish plants
from animals. And the same must be said of all
apparently more valid distinctions, drawn from
chemical analysis of their respective tissues.
There is, in short, no definable character, or
combination of characters, common to all plants
and foreign to all animals, or vice versa.

Some persons, influenced by these considera-
tions, have gone so far as to assert that there is
no real line of demarcation between the animal
and vegetable kingdoms, and that both merge in-
sensibly into each other. Others have attempted
to prove the existence of three distinct kinds of
organised bodies, namely, plants, animals, and in-
termediate beings. Neither of these extreme
views can be adopted. The popular opinion that
there are two and only two great divisions of
organic forms, distinct from one another, has been
amply confirmed by the combined researches of
our most able and trustworthy investigators, who
believe that a line of separation between these
two divisions does exist, though they may not be
able precisely to define its limits. For it should
be borne in mind, that the real difficulty now
under consideration lies, not so much in our ca-
pability to determine whether any organism which
may be offered for our inspection be a plant or an
animal, since this, to any competent and unpre-
judiced observer, is seldom a matter of impossi-
bility, but in framing such a definition as will
embody our abstract conception of those essential

INTRODUCTION. XV

and exclusive features, whicli separate the or-
ganic world into two distinct spheres of exist-
ence.

Nor should it be forgotten that those outward
manifestations, which result from the presence of
a locomotive apparatus and a material recipient
of sentient impressions, though not exhibited by-
all animals, are by no means, on this account, less
worthy of being considered as the most striking
characteristics of animal life, of which, indeed,
they are the peculiar ^products. In this point of
view they were regarded by Aristotle"^, who tias
beautifully contrasted such active operations with
the profound slumber in which the life of vege-
tables is plunged.

But of all the artificial distinctions which serve
to separate plants from animals, none will be
found more remarkable than those which are
based, either on the nature of their respective
nutrient materials, or the mode in which such
materials are appropriated. The food of plants ^^A'
consists, for the most part, of the inorganic com-
pounds, water, carbonic acid, and ammonia, to-
gether with minute quantities of a few mineral
substances, usually to be found in most fertile
soils. The Fungi, and other parasitic vegetables,
are supposed to offer only apparent exceptions to
the truth of this statement. Animals, on the
other hand, require for their subsistence organised
matter, which has been previously stored up in
the bodies of other living beings. Again, plants

XVI INTEODUCTION.

imbibe their nutriment by means of absorbent
organs situated on the exterior of their bodies,
while the food of animals is first received into an
interna] digestive cavity, there to be subsequently
elaborated. And even the greater number of
those simple animal beings, in which no definite
internal cavity can be perceived, would seem to
have the power of forming one, as it were, extem-
poraneously, whenever its presence is called for to
supply the wants of the organism.

Every animal, as a livir.g being, possesses a
definite form, which is itself the product of a
number of definite parts or organs. In the higher
animals, the number of these dissimilar parts
attains its maximum. In others, no such com-
plexity of structure is observable, and there are
not wanting some animals, whose organisation is
so exceedingly simple, that any differentiation of
the body into separate parts can vdih difficulty be
determined. There are also many animal forms
of comparatively humble position, in which the
entire fabric consists, not of a few distinct organs,
each performing its special function, but of nu-
merous parts similar to one another, and all ful-
filling the same purpose. Such organisms are
said to exhibit a tendency to a "vegetative (or
irrelative) repetition of similar parts," ^ an expres-
sion which will be found convenient in practice,
provided it be borne in mind that the "similar
parts " are not Histinct individuals.

I^^TRODUCTION. XVll

The several organs of which animal forms are
made up are all mutually related, or, in other
words, certain leading peculiarities of structure
are invariably found to co-exist with one another.
This is termed the " correlation of forms." Some
naturalists, not content with recognising the fact
of such co-existence, have forsaken the true scien-
tific method, and have sought to discover a causal
relationship between the organs thus associated
together. But morphology furnishes no answer
to these futile inquiries.'*

"VVe compare the organs of different animals
with a view to ascertain whether they agree in
structm'e with one another. When such is the
case, the corresponding organs are said to be
*' homologous." By some the word "morphology"
is employed in a restricted sense, to signify the
study of homologous organs. And it may here
be mentioned that the term Histology has been
applied to that branch of morphological science
which is specially connected with the investiga-
tion of minute structure.

When two organs perform the same function,
they are said to be " analogous " to one anothor.
It is necessary to draw an important distinction
between analogy and homology. For it is pos-
sible that two organs may correspond with one
another in both structure and function, or in
structure only and not in function, or again in
function only and not in structure.

a

XVlll INTRODUCTION.

Under the title of the " Balancing of Organs "
some morphologists have sought to establish a
principle which may lead to the adoption of erro-
neous conclusions. This principle, rightly stated,
is as follows : — The excessive development of
one organ is often accompanied by a proportional
deficiency in some other organ connected with it.
But to this rule there are many exceptions, and
in no case can it be proved that the atrophy or
deficiency of one organ is the result of the extra-
ordinary development of the other.

The several functions, or vital actions, of ani-
mals may be conveniently arranged under three
groups, namely : —

1. Those which are subservient to the growth
and maintenance of the organism — Functions of
Nutrition.

2. Those which have reference to the continu-
ance of the species — Functions of Re/production.

3. Those which enable the animal to perform
movements and become conscious of external im-
pressions — Functions of Relation.

Of these, the Functions of Nutrition and Ee-
production, being common to all organised beings,
are sometimes designated " Functions of Ortranic
or Vegetative Life," while the Functions of Rela-
tion are distinguished by the title of ''Animal
Functions."

The lowest form of animal life with which we

INTRODUCTION. XIX

are acquainted lias the power of maintaining its
existence and increasing in size ; it likewise exe-
cutes perceptible movements, and gives rise to
other beings similar to itself. So also is it with
the most highly organised animal. What then is
the natm-e of the physiological distinction between
both?

In the simple animal being to which we have
alluded it can scarcely be said that distinct organs
exist, all parts of the body appearing to possess
the power of performing, when called upon, any
one of the necessary functions. In other animals,
we recognise the presence of separate instruments
for the discharge of each of the three great groups
of functions above enumerated. In others, again,
we find that one or more of these is resolvable
into what may be termed " secondary functions,''
to each of which a special organ has been allotted.
Finally, we meet with animals in which this "spe-
cialisation " of the functions and multiplication of
dissimilar parts reaches its utmost extent. When
such is the case, it is not difficult to show that the
various vital actions are accomplished with a de-
gree of completeness and efficiency not observable
in those humble organisms whose position is at
the base of the animal scale. All this is said to
be in accordance with the principle of the physio-
logical division of labour.

In the higher animals the nutritive processes

are subdivided into functions of prehension, mas-

a 2

XX IKTROLUCTION.

tication, insalivation, deglutition, digestion, ab-
sorption, circulation, respiration, exhalation, ex-
cretion, secretion, and nutrition proper. It may
further be noticed that these functions, being from
their very nature necessary to the maintenance of
the organism, are performed throughout the entire
period of its existence.

It is not so with the Functions of Reproduction,
the demand for which is often not manifested
until the life of the individual has approached
maturity, and even after that period it is not con-
stant, but occasional. Moreover, the discharge of
these functions, so far from being favom-able to
the maintenance of the organism, is, on the con-
trary, rather opposed to it, and it has even been
observed that in some animals death always occurs
shortly after the performance of the generative
function.

The true generative act consists in the produc-
tion of germs, and their subsequent contact with
other bodies, termed * spermatozoa.' The young
germ is usually surrounded by a mass of nutrient
matter (or yolk), and the whole together consti-
tutes an *ovum.' The contact of the ova and
spermatozoa is termed 'fecundation.' Ova and
spermatozoa may be generated in the same or in
different individuals. Hence arises the distinction
of sex ; the power of producing ova being peculiar
to the female, while the formation of spermatozoa
devolves upon the male. It is well known that

INTRODUCTION. XXI

the two sexes are, in most cases, distinguished by
various external peculiarities.

The independent being which results from the
complete development of a fertilised ovum may
subsequently multiply itself in various modes
which have been grouped together under the
common name of "asexual generation." These
are all reducible to two processes, namely, * fis-
sion,' or the division of the body into separate
parts, and 'gemmation,' or the formation of
buds. Gremmation may be either internal or
external. 'S^Tien the products of the latter remain
in connection with the parent organism, we are
furnished with an illustration of the tendency to
a vegetative repetition of similar parts ; but should
they separate from it in the form of seemingly in-
dependent beings, it then becomes difficult to dis-
tinguish between the results of fission and gem-
mation. Both of these processes are most easily
observed among the lower animals.

Care must be taken not to confound the imme-
diate offspring of the true generative act with the
detached products of fission and gemmation. The
former alone are properly denominated "indivi-
duals." The latter may be known by the name of
" zooids." Those who apply the term individual to
these last are guilty of employing it in two distinct
senses, for among the higher animals the apparent
individual is always " equal to the total result of
the development of a single ovum." ^

a 3

XXll INTRODUCTION.

It often happens that the zooids resulting from
■fission or gemmation are very dissimilar in out-
ward appearance to the organisms by which they
were produced, while they possess the power of
giving rise, by a true generative process, to be-
ings exactly resembling the latter. In order
to explain these phenomena, certain naturalists,
ignorant of the distinction between "zooid de-
velopment" and sexual generation, devised the
ingenious theory of " alternation of generations."
But, from what has been said, it must appear
that, in the instances referred to, there is not an
alternation of two (or more) distinct generative
acts, but rather an alternation of true generation
with either gemmation or fission.

The functions of Eolation may be di\aded into
those of the muscular apparatus and those of the
nervous system.

Were it possible for us to become acquainted
with the structme and functions of any organism,
our knowledge of its natm-e would still be im-
perfect so long as we remained ignorant of its
life history. Hence the necessity of the study of
Development, which investigates the primitive
characters of living beings, and the changes which
they undergo in passing from the embryonic to
the adult condition. Morphology, it may be said,
teaches us what an animal ^s, Physiology what it

INTRODUCTION. XXlll

does, Development what it luas, and how from
what it was it came to be what it is.

The study of development is, however, not
merely desirable in itself; it is also absolutely
requisite in the determination of homologies.
Organs are usually said to be homologous when
they correspond with one another in structure,
and are connected with similar parts of their re-
spective fabrics. But it would appear that these
tests are sometimes fallacious, and, in the case of
adult organisms, their application often becomes
impossible. It is therefore necessary to compare
the organs of different animals in their simplest
condition, and to trace the several stages through
which they pass, before it can be said that they
agree with one another. And the same rule may
be extended to the entire animals of which such
organs form part.

A knowledge of development alone is capable
of furnishing a solution to the inquiry. How far
may unity of organisation be predicated of all
animals ? The answer is, in their primitive con-
dition only, since the study of Morphology clearly
shows the existence of distinct plans of structure
among adult animals. All these start, as it were,
from the same point, namely, the condition of the
germ, and from this they rapidly diverge, each
successive step in their development tending to
separate them farther from one another. To the

a 4

XXIV INTRODUCTION.

researches of the great Von Baer we are indebted
for the enunciation of this important principle.^

Since the number of animal beings is exceed-
ingly great, it seems needless to insist upon the
necessity of arranging them into groups, so that
they may be readily compared with one another*
But it must not be inferred that it is the sole or
even the chief end of classification, so to facilitate
reference that the relative position of any animal
may be at once determined by means of easily re-
cognisable external characters. Systems which
propose to effect this object alone are termed
artificial, and of such systems there may be se-
veral. True classification is contradistinguished
by the term natural, since it may be defined as
the right appreciatiooi of the mutual relations
of animals, as dependent upon those characters
and capacities tvhich they have received from
their Creator, And as there is but one Author of
Nature, so also there can be but one true interpre-
tation of that Author's plan, though from insuffi-
cient knowledge and other causes, the various
attempts to frame a natural classification which
have hitherto been proposed, all differ more or
less from one another in matters of detail.

We have already seen that animals may differ
from one another in the varying complexity
of their organisation. Differences of this kind,
which are usually obvious, were supposed, by the

INTEODUCTION. XXV

earlier naturalists, to furnish sufficient characters
whereby to distinguish the primary divisions of
the animal world. It was afterwards ascertained
that these tests, however suitable they might at
first sight appear, were applicable only within cer-
tain limits. For it is easy to select two animals,
in all essential features strikingly dissimilar,
though upon examination it will be found impos-
sible to decide whether the organisation of one be
superior, as a whole, to that of the other. Hence,
all arrangements which exhibit the animal king-
dom as a continuous series, leading step by step
from the humblest of all animal forms to those in
which the specialisation of functions is most strongly
marked, are evidently unnatural.'^ For as there
are two distinct points of view from which all
animals may be considered, so also one animal
may differ from another either as to the greater
or less complexity of its structure, or the general
^lan upon which its structure has been framed.
Every animal, as Huxley has well observed, may
be regarded as the resultant of two tendencies, the
one physiological, the other morphological.^

By applying a process of generalisation to the
numerous facts which the study of morphology
has disclosed, we are led to the conclusion that
five ultimate plans of structure may be traced
among animal forms. And accordingly the entire
animal kingdom may be divided into the same
number of primary groups, technically known

XXVI INTRODUCTION.

Tinder the names of sub-kingdoms, branches, or
departments, namely, —

Vertebrata,

MOLLUSCA. AnNULOSA.

Ccelenterata,
Protozoa.

Sub-kingdoms are divided into classes, classes
into orders, orders into families, families into
genera, and genera into species. It is usual to
state that, "the species is a living form represented
by individual beings, which reappears in the pro-
duct of generation with certain invariable cha-
racters, and is constantly reproduced by the ge-
nerative act of similar individuals."^ Bat it
cannot be said that this definition is altoo-ether
unimpeachable.

It sometimes happens that between different
individuals, known to belong to the same species^
certain distinctive peculiarities are observable.
When such peculiarities are strongly marked, the
individuals which possess them are denominated
varieties. Permanent varieties, i, e. those which
always produce offspring similar to themselves,
are distinguished by the name of races.

The question how far individuals belonging to
the same species may vary is intimately con-

INTEODL'CTION. XXTll

nected with that department of Zoology which
treats of the Distribution of animal beings. For
if it can be shown that animals are capable of be-
coming modified to an indefinite extent by the
physical conditions under which they are placed,
the following conclusions are inevitable :

1. That many of the apparently dissimilar ani-
mal forms found in difi'erent regions of the globe,
are to be viewed as varieties of the same species,
the differences between them being due to cor-
responding variations in the external agencies to
which each has respectively been subjected.

2. That one species may pass into another, or,
in other words, that species have no existence.

But since little positive evidence can be lu^ged
in favour of these conclusions, it seems desirable,
for the present at least, to reject them as unsatis-
factory, " for it is more probable that species
should have been created with a certain decrree of
variability, than that mutability should be a part
of the scheme of nature." It cannot, however, be
denied ^ hat the tendency of several species to
form varieties, is much greater than many natu-
ralists are accustomed to admit, ^o

In considering the subject of distribution, it is
necessary, as far as possible, to separate the facts
of the science from the various theories which
have been devised to explain them. The former,
if rightly observed, may be accepted, since they

XXVlll INTRODUCTION.

exist in nature. The latter must be received
with caution, since they are, for the most part,
pure hypotheses.

Numerous observations show that some ani-
mals are very widely distributed, while others are
restricted within narrow limits. Again, some
districts contain a fauna {i. e. animal population)
peculiar, or nearly so, to themselves ; whilst
others are peopled almost exclusively with de-
rived species.

To account for these, and numerous other facts
of a similar kind, it has been assumed that all the
individuals of each species proceeded from one
originally created pair ; or, in the case of bisexual
organisms, from a single parent. Each species
must, therefore, have been at first confined within
a very limited area ; but being endowed with a
power of diffusing itself, its descendants, after the
lapse of time, became dispersed to a greater or
less extent. ^^

There are, however, various causes which would
tend to keep in check the migration of animals.
Among these, an inability to exist outside a
certain range of temperature is not the least im-
portant. For it has been proved that contiguous
areas, with different climates, are inhabited by
different species of animals. On the other hand,
the effect of climate in determining the distri-
bution of organised beings has been, in many

INTEODUCTION. XXIX

instances, exaggerated. Other natural barriers,
even more powerful, interpose to prevent the too
wide-spread diffusion of both plants and animals.
The several facts which may be deduced from
observation of the distribution of animals in Space,
fall under the three following categories : —

1. The relations of animals to the elements in
which they live.

2. Their lateral (geographical) distribution.

3. Their vertical (bathymetrical) distribution.
The distribution of animals in Time forms a

distinct subject of inquiry, the consideration of
which can only be entered on with profit by those
who possess some acquaintance with the science
of physical geology. It will, therefore, be suf-
ficient here to state the following generalisa-
tions : —

Every species has a definite distribution in
Time.

Each of the great geological epochs contained
an assemblage of forms, different from one
another, and the present.

In the older geological formations, there ex-
isted representatives of each of the five great
divisions of the animal kingdom.

The animal remains found in these ancient
formations, though referrible to the same classes,
belonged, in many cases, to orders, families,
genera, and species, different from those now

XXX IXTRODUCTION,

living. In rocks of more recent date, the orders
and families correspond to those at present
existing, though the genera and species still
remain dissimilar. Grradually, even these ap-
proximate ; first the genera, and, finally, the
Rpecies becoming identical with those of the
present da}^

XOTES.

T. In the 'Principles of Psychology,' by Herbert Spencer,
various definitions of Life are discussed.

2. Aristotle — m^, lumv Tivio-ioj;.

3. Owen — ' Lectures on the Comparative Anatomy and Physio-
logy of the Invertebrate Animals.'

4. See Huxley — ' On the Method of Paleontology,' (in Annals
of Natural History, 1856.)

5. Huxley — 'Report upon the Researches of Professor Miiller
into the Anatomy and Development of the Echinoderms,' (in Annals
of Natural History, 1851.)

6. Von Baer — 'Ueber Entwickelungs-geschichte der Thiere.'
See also Carpenter — ' Principles of Comparative Physiology.'

7. CuviER, in a Paper read before the French Academy, first
clearly announced the existence of distinct plans of structure in the
Animal Kingdom. See his ' Regne Animal,' 2^^ edition.

8. Huxley — ' Lectures on General Natural History,' published in
the Medical Times and Gazette.

9. J. Mt'LLER — ' Handbuch der Physiologic des Menschen.'

10. J. D. Hooker and T. Thompson — ' Introductory Essay to
the Flora Indica.'

1 1. See Lyell — ' Principles of Geology ;' and Forbes — ' On the
Connection between the Distribution of the existing Fauna and Flora
of the British Isles, and the Geological Changes vrhkh have affected
their Area,' &c. (in the Memoirs of the Geological Survey of Great
Britain, 1846.)

THE

SUB-KINGDOM

PROTOZOA.

P E 0 T O Z 0 A.

CHAPTER I.

PROTOZOA.
1, General characters. — 2. Classification.

I. Cresieral eliaraeters. — The sub-kingdom
Protozoa includes a number of animal beincfs of
simple organisation, many of which have, until
recently, been associated with the lower members
of the vegetable kingdom. Hence no good ge-
neral definition can be given of this sub-kingdom,
the several forms which it includes being distin-
guished from those which are placed in the four
remaining zoological departments by chiefly nega
tive characters. In none ot the Protozoa do we
find a nervous system or organs of sense, and,
in many of- these animals, the existence of a
distinct alimentary apparatus has yet to be ascer-
tained.

In the substance of the bodies of most Protozoa
a minute solid particle known as the ' nucleus ' is
found to occur ; and, in addition to this, the pre-
sence of certain clear spaces termed 'contractile
vesicles ' may, in some species, be traced,

B

2 PROTOZOA.

In a large number of the Frotozot true sex-
ual reproduction has not yet been proved to take
place.

In habit the Protozoa are almost exclusively
aquatic. Some attain to an appreciable, and even
(in the case of the Sponges) considerable, size; but
by far the greater number are minute, and hence,
notwithstanding their abundance, the ignorance
which still prevails as to their real nature.

2. Classiiieatlon. — The following animal
groups are included in this sub-kingdom, viz. : —

J. Rhizopoda,

2. Polycystina,

3. Spongidcey

4. ThalassicollidcB,

5. Gregarinidce,

6. Infusoria,

The presence of a mouth is characteristic of the
Infusoria, and hence the remaining Protozoa are
sometimes designated by the collective appellation
of ' Astomata.^

KHIZOPODA.

CHAPTER 11.

RHIZOPODA.

I. Type of the group : Amoeba. — 2. Nature of Rhizopoda. — 3
Rhizopoda allied to Amoeba. — 4. Classification of Rhizopoda. — 5
Foraminifera. — 6. Classification of Foraminifera. — 7, Unilocular
Foraminifera. — 8. Polythalamia. — 9. Structure of the shell in
Foraminifera. — 10. Technical terms. — 11. Distribution of Fora-
minifera in Space. — 12. Distribution of Foraminifera in Time. —
If. Size of Rhizopoda. — 14. Development of Rhizopoda.

I. Type of the group : Amveba. — In order
to understand the true nature of the Rhizopoda it
will be necessary, in the first place, to become
acquainted with those characters which are fur-
nished by the examination of some typical form.
The most easily procured of all Rhizopods is,
perhaps, the ATYioeha, a minute animal not un-
common in most ponds or infusions {fig* i).

WTien first placed under the microscrope the
Ainoeba presents the appearance of a globular mass
of semitransparent jelly, destitute of any apparent
organisation. This seemingly helpless being soon,
however, commences to show signs of life by push-
ing out in various directions portions of the jelly-
like substa,nce of which its body is composed. By
expanding one of these prolongations, and then
drawing after it (or rather into it) the remainder
of its body, the Amoeba slowly advances, in a some-
what irregular manner. The gelatinous processes
thus protruded have received the name of ' pseu-
dopodia,' from their subservience to the function
of locomotion. But this is not the only pui'pose
which they serve. Should the Amoeba, in its pro-
gress through the water, come in contact with any

B 2

EHIZOPODA.

foreign substance of small size, the latter is tena-
ciously grasped by the pseudopodia, whicb coalesce
around it, and thus the morsel soon becomes en-

Fig. I.

Am(E3A kadiosa : — a, young Amceba, with five pseudopodia
protruded ; b, older specimen ; c, peculiar variety of do. ; v,
the nucleus.

closed in the interior of the body. There is no
true oral orificej and the mode in which deglu-

EHIZOPODA. 5

tition is performed by the Amoeba may not inaptly
be illustrated by forcing a stone into the interior
of a lump of clay or similar plastic material. The
power of selection possessed by the Amwba would
seem to be but slight, either as to the quantity or
quality of its food. Inorganic particles, such as
sand, are frequently ingested along with its more
proper aliment. Sometimes the body of the
Amoeba appears as a mere transparent film in-
vesting the substance swallowed, and it occasion-
ally happens that it becomes impaled on the sharp
point of some projecting object. The indigestible
remains of the food are finally pushed out through
some part of the gelatinous body.

In the interior of the bodies of most Amoeboe a
central solid particle or ^ nucleus ' (v) may be
observed, and, at certain times, one or more clear
spaces or * vesicles ' may also be noticed. These
contractile spaces are not permanent, but are seen
to appear and disappear suddenly at more or less
regular intervals. The colourless fluid, which they
contain when dilated, would seem to be furnished
during the process of digestion.

Physiologically, the Aiinoeba may be regarded as
the lowest of all animal forms, destitute of distinct
organs, any part of its gelatinous body being ca-
pable of performing the functions of locomotion,
digestion, &c., for the discharge of each of which
a special, and often highly complicated, apparatus
is set apart in the case of many of the higher
animals. But, notwithstanding this simplicity
of structure, several naturalists deem themselves
justified in regarding the more permanent varieties
of Amoeba as so many distinct species ; several of
which have been described and figured byAuerbach.

B 3

RHIZOPODA.

In the body of one of these {A. bilimbosa), the
existence of starch granules has been detected by
the same observer.

3. IVature of Rhizopoda. — The structure
of the remaining Ehizopods differs in no essential
respect from that of Am<jeba, In all, the body is
composed of the same simple gelatinous substance
or ' sarcode,' as it has been termed by Dujardin,
and in all, locomotion is performed by means of
Ijseudopodia. From this circumstance, the group
derives its name.

3. Rhizopoda allied to Amceba. — The so-
called " sun animalcule " (Actinophrys), by some
placed among the Infusoria, may be regarded as
closely allied to Amoeba. The form of its body
( fig. 2, a) is that of a depressed sphere, furnished
with a number of filiform pseudopodia radiating

Fig. 2.

Various forms of Rhizopoda : — a, Actinophrys sol in the act
of feeding; at d is shown a captured Infusorium which has just
entered the substance of the body ; b, portion of the same, mag-
nified 450 diameters ; c, Arcella acuminata; d, Difflugia proiei"
formis.

in all directions. These pseudopodia are usually
somewhat longer than the diameter of the body.

EHIZOPODA. 7

and are far less mutable than the same parts in
Aoiioeba. The body of Actinophrys, when mag-
nified {fig, 3, 6), is seen to be composed of a
simple homogeneous sarcode substance, filled with
granules and ' vacuoles,' in the midst of which a
true ' contractile vesicle ' may, in most cases, be
readily perceived. The mode in which this Ehi-
zopod takes food is peculiar, and has been care-
fully observed by Kolliker. Should a small Crus-
tacean, Eotifer, or any other of the minute active
animals upon which the Actinojph^s is accus-
tomed to feed, come in contact with one of the
radiating filaments, it soon adheres to the latter,
which slowly shortens until it approaches the
surface of the body, the filaments in its neigh-
bourhood bending around it, so that the prey be-
comes surrounded on all sides. The pseudopodia
then gradually diminish in length, until that by
which the prey was first seized altogether disap-
pears. At this spot a depression begins to be
formed, in which the captured animal is lodged
(fig. 2, a, 6). This depression becomes deeper
and deeper, the pseudopodia around it again elon-
gate, and finally its outer edges coalesce, so that
the prey becomes enclosed in a cavity. Here it
remains until digested, after which the cavity
contracts, and finally disappears. But should any
indigestible particles remain, these are expelled
by renewed contractions of the sarcode body, usu-
ally in the same direction by which they were
originally taken in.

In both of the Ehizopods already noticed the
body is completely naked. In some -4mce6ce, in-
deed, its outer portion would seem to possess a

6 4

8 EiriZOPODA.

certain degree of consistence, so as to serve as an
envelope for the protection of the softer sarcode
within. But in Difflugia we find it invested with
a membranous 'carapace' or 'lorica/ of an oblong
or oval figure, from the terminal aperture of which
the pseudopodia are protruded {^fig. 2, d). In
Arcella the carapace assumes a discoid or hemi-
spherical form {fig. 2, c), with the single narrow
orifice placed on its flat surface. In both of these
Khizopods the surface of the carapace often ex-
hibits tubercles or depressions, or has particles
of sand, &c., imbedded in its substance ; and in
Arcella the margin is frequently provided with
long spinous prolongations. The curious Pam-
phagus, described by Bailey, would seem to form
a connecting link between these Ehizopods and
Amoeba. Like the latter, it is destitute of a cara-
pace, but it agrees with Arcella and Difflugia in
having the pseudopodia protrusible from one ex-
tremity only of the body. It undergoes the most
extraordinary mutations of form, which are chiefly
the result of its habit of swallomng almost every
substance with which it comes in contact. Hence
the appropriate name (P. niutabilis) conferred on
this Ehizopod by its late discoverer.

4. €lassi@catl€»ia of MMzopoda The Ehi-

zopoda may be arranged under two sections,
Amoebea and ForarYiinifera. The first of these
may be again subdivided into two minor groups :
I. Amoebina, including those Ehizopods which
have the body naked, viz. Amoeba, Actinophrys,
and Pa7)iphagus ; and 2. Arcellina, which con-
tains Difflugia and Arcella. All these Ehizopods

EHIZOPODA. 9

were formerly placed among the Infusoria. They
chiefly inhabit fresh water.

^. Foramitiifera. — The Foraminifera differ
from the ATUoehea in being -usually invested with a
calcareous covering or ' shell,' which is sometimes
simple, but more frequently consists of an aggre-
gation of separate chambers or ' loculi ' commu-
nicating with one another by means of minute
apertures. In accordance with this character, the
name Foraniinifera has been given to the group.
The appearance presented by these shells (Jigs. 3,
and 4), both as regards outward configuration and
internal arrangement, is often exceedingly com-
plicated; and, in many cases, the same species
presents itself to our notice under a wonderful
diversity of forms. Accordingly, those naturalists
by whom the Foraminifera were first studied,
misled by external characters, assigned these
animals a position far higher than that to which
their internal structure entitled them. Their true
nature was first explained by Dujardin, who
showed that the animals inhabiting these cal-
careous shells differed in no essential respect from
Amoeba or Avcella, and that, like these forms,
their bodies were composed of a homogeneous
sarcode substance {fig. 3, g). In some Fora-
ininifera, this sarcode body is found to assume a
bright red colour. The pseudopodia of these
animals are usually longer and more slender than
those of the Amoehea.

6. Classification of ForamiaBifera. — By

D'Orbigny the Forarainifeva have been divided
into six " orders," viz. : —

10 EHIZOPODA.

1. Monostega. — Body consisting of a single seo"-

ment : shell of one chamber.

2. Stichostega. — Body composed of segments dis-

posed in a single line : shell consisting of a
linear series of chambers.

3. Helicostega. — Body consisting of a spiral series

of segments ; shell made up of a number of
convolutions.

4. Entomostega. — Body consisting of alternate

segments spirally arranged: shell chambers
disposed on two alternating axes forming a
spiral.

5. Enallostega. — Body composed of alternate

segments not forming a spiral : chambers ar-
ranged on two or three axes which do not
form a spiral.

6. Agathistega. — Body consisting of segments

wound round an axis : chambers arranged in
a similar manner, each investing half the
entire circumference.

All these orders, with the exception of the first,
are sometimes designated by the collective appel-
lation of ' Polythalamia.^

A somewhat different arrangement has been
adopted by Schultze, who divides the Polythala-
inia into three sections, viz. : —

1. Helicoidea, including those forms in which

the scAT^eral chambers of the shell are ar-
ranged in a convolute series :

2. Rhahdoidea, in which they are placed in a

direct line : and,

3. SoToidea, where they are disposed in an irre-

gular manner. {Vide Table, p. 11.)

KHIZOPODA. 11

TABLE

SHOWING SCHULTZE'S AERANGEMENT OF THE

RHIZOPODA.

A NUDA.

(Contains the genus Amceba.)

B. TESTACEA.

(Includes Forajunifera and Arcellina.)

1. Honothalamia.

( = MoNOSTEGA, D'Orbigny + Arcellina).

3. Polythalamia.

f Helicostega, D'Orb.
+
Entomostega, D'Orb.

+
Enallostega, D'Orb.
+
t Agathistega, D'Orb.

b. RHABDOIDEA = (Stichostega, D'Orb.).

C. SOROIDEA. (Contains the genus Acervulina, Sch.)

a. HELICOIDEA

12 EHIZOPODA.

All these arrangements may, however, be
regarded as premature, pending the result of
further investigations into the internal structure
of the shell, a more extended acquaintance with
which must form a necessary prelude to the
proper classification of the Foraminifera. Since,
moreover, we are unacquainted with the entire
life-history of any one of these animals, it is
evident that the time has not yet arrived for pro-
posing such an arrangement.

The truth of these observations ^^^ll further ap-
pear when we consider that in the Foraininifera,
more perhaps than in any other group of animal
forms, is the same species liable to be influenced
by age, by the different circumstances in which it
is placed, or by both of these causes combined.
To assign the limit to which these variations may
extend is, in many cases, at present impossible.
For it has been fully proved, in more than one
well ascertained instance, that two or more varieties
of the same species obtained from distant localities,
or from the same locality, but at different stages
of gro^vth, may present such dissimilarity of out-
ward aspect as to require, for the determination of
their specific identity, the examination of many
hundred individual specimens, each gradually
passing into the other. Hence it is easy to con-
ceive how, by folloAving too closely the arrange-
ment of D'Orbigny, different varieties of the same
species have been placed in separate orders ; the
principle on which his system has been founded,
namely, the direction of growth of the shell,
being obviously insufficient for the purposes of
classification.

rxHIZOPODA.

13

Fig, 3.

Various forms of Foraminifera : — a, Lagena striata; a'
Nodosaria rugosa ; h, Marginulina { = Cristdluria) raphanus ;
h\ longitudinal section of shell of do. ; c, Pulystomella crispa,
with its pseudopodia protruded ; d, Nummidites lenticularis,
shown in horizontal section ; e, Cassidulina Icevigata ; f, Textu-
laria globuhsa; gr, Mdlolina seminulum ; g', animal of Miliolina
removed from its shell.

7. Unilocular Foramfnlfera The Uni-
locular Foraraimfera may be said to constitute an
intermediate group between the Polythalamia and
Arcellina ; the form denominated Gromiia, for
example, scarcely differing from Difflugia or Ar-
cella, save in the greater length and tenacity of its
pseudopodia. A better example of these Ehizo-
pods is furnished by Lagena, which may be suffi-
ciently characterised by the beautiful flask-like
form of its shell {Jig, 3, a), the external surface of

14 RHIZOPODA.

which frequently assumes a fluted appearance,
caused by the presence of numerous longitudinal
striae. In addition to the outlet at the mouth of
the shell the entire surface of the latter is perfo-
rated by a number of exceedingly minute aper-
tures, through which the pseudopodia are protrii-
sible. Entosolenia may be compared to Lagena
with the tubular neck inserted into the hollow in-
terior of the shell,

8. Polytha lamia. — Among the Polythala-
onia the modifications in external confiofuration
assumed by the shell would seem to be almost
without limit. In Nodosaria [Jig. 3, a') it pre-
sents the aspect of a cylindrical beaded rod, which
in Lingidina becomes compressed, and in Denta-
lina more or less curved, whilst in Frondicularia
the peculiar sagittate form of the chambers will
be found a distinctive test.

The term 'nautiloid' has been applied to a
large group of multilocular Khizopods, the shells
of which present externally a remarkable resem-
blance to those of a well known group of Mollus-
cous animals, including the Pearly Nautilus and
its numerous extinct allies. It was this similarity
of outward form which led the earlier naturalists
to refer the Foraminifera to the class of Cephalo-
poda ; a view of their nature which received the
sanction of Cuvier and D'Orbigny, and continued
to be generally adopted until the year 1835,
when its incorrectness was fully demonstrated
by Dujardin, who was the first to point out the
simple nature of the animal body which occupied
the interior of these many-chambered shells.
These nautiloid forms constitute an extensive

RHIZOPODA. 15

section of the order Helicostega of D'Orbigny.
It has since, however, been shown that many
Foraminiferous shells which commence their
growth upon the spiral planj e. g. Gristellaria,
ultimately assume a straight form, so as to resem-
ble Nodosaria {fig. 3, 6, h'). Examples of nau-
tiloid Ehizopods may be found in Polystoraella
{fig. 3, c), and in the well-known fossil Nummu-
lites {fig. 3, d).

In Cassidulina {fig. 3, e) and its allies, each of
the chambers of which the spiral shell consists is
furnished with two surfaces of unequal size,
which are alternately presented to opposite sides
of the shell. Other modifications of the Polv-
thalamous structm'e are presented by Textularia
{fig. 3,/), and Miliolina {fig. 3, g), the nature
of which will best be understood when we come
to consider the mode of growth of the shell.

g. I^ltructure of the §hell in Foraniiwifera.

— The structure of the shell has been ably inves-
tigated by Drs. Carpenter, Williamson, and others,
whose combined researches have proved that its
many complex forms all result from continuous
processes of gemmation, and that the several
varieties of these are dependent on corresponding
variations in the plan upon which this gemmation
is conducted. For all the multilocular Ehizopods
consist at first of but a single chamber. Should
the latter put forth another chamber similar to
itself, and in a direct line with the axis of its body,
this process, repeated several times, would give
rise to such a form as Nodosaria, in which
the original orifice of the first chamber serves as
an aperture communicating between it and the

16 RHIZOPODA.

second, so that the several portions of the sarcode
body contained in the entire series of chambers
are all united by means of connecting bands
or ' stolons,' of the same substance {fig. 3, h'). If
the successive chambers gi-adually increase in
size, a conical shell will be produced. If, again,
each of the newly formed chambers, instead of
being developed in the axis of its predecessor, be
turned slightly to one side of the latter, the whole
series will assume a curved figure, and this may be
carried to such an extent as to confer on the entire
shell a spiral or convolute forrii. If the several
convolutions of one of these spiral forms all lie in
the same horizontal plane, as in Polystomella or
Kumrmdites {fig, 3, c and l/), the shell is said to
be ' equilateral.' But if the successive chambers be
developed on one side of the plane of the first
chamber, so that the spiral passes obliquely round
an axis, the shell assumes a more or less pyra-
midal form, and is termed * trochoid ' or ' inequi-
lateral.' These latter terms may also be applied to
such shells as Textularia {fig. 3, /), which appa-
rently consist of two or more oblique longitudinal
rows of chambers, but in reality differ only from
the true spiral forms in the smaller number of
chambers which occur in each of the convolutions.
A different mode of growth prevails among the
MiliolincE. These are usually somewhat oblong in
figure, each of the newly formed chambers being
equal in length to the entire shell, so that, as
growth proceeds, the terminal orifice is alternately
transferred from one end of the shell to the other.
Hence, in these shells, the addition of successive
segments has been compared to the winding of the
thread round a ball of worsted {fig. 3, g).

EHIZOPODA. 17

In addition to ttie terminal orifice, which we
have hitherto regarded as the sole growing point of
the shell, many Foraminifera have the external
surface of the latter perforated with numerous
minute apertures, through which thread-hke
extensions of the sarcode body can be protruded
{fig. 3, c); and it is not improbable that, by
the coalescence of several of these, a layer is
formed which may serve for the deposition of cal-
careous matter in the form of spines or other
peculiarities of surface configuration. It would
seem, however, that in Faujasina, Operculina,
and certain other Polythalamia, these foramina
are not to be regarded as simple apertures in the
w^alls of the chambers, but rather as the orifices of
a peculiar system of ' interseptal ' canals, which
after ramifying between the walls of contiguous
chambers proceed directly to the innermost portion
of the shell, serving to bring those parts of the
sarcode body which are contained in the latter
into immediate communication with the exterior.
In Num/mulites and other fossil forms these canals
have been observed to increase both in number
and complexity of arrangement ; for here, in addi-
tion to the regulai' series of chambers, there exists
an 'interstitial skeleton' for the nutriment of
which this increased development of the * canal
system,' would appear to be required. Hence
it has been said that these Polythalamia present
us with the highest and most fully developed type
of Foraminiferous structure.

A mode of growth distinct from any of the
preceding has been observed by Dr. Carpenter
to take place in another group of Foraminifera,
of which Orbitolites may be regarded as the type.

C

18 EHIZOPODA.

If the circular flattened disk of one of these fonns
{fig. 4, a) be submitted to microscopic examina-
tion, a series of rounded elevations disposed in
concentric annular bands round a central " nu-
cleus " may be observed on its surface, whilst its
margin is seen to consist of an undulating succes-
sion of rounded projections alternating with de-
pressions, each of the latter being provided with
a single orifice. On more careful examination,
we find that each of the rounded elevations con-
stitutes the upper surface of a chamber or cell,
*' which communicates by means of a lateral
passage with the cavity on either side of it in the
same ring ; so that each circular zone of cells might
be described as a continuous annular passage,
dilated into cavities at intervals. On the other
hand, each zone communicates with the zones
that are internal and external to it, by means of
passages in a radiating direction ; and it is curious
that these passages run, not from the cells of the
inner zone to those of the outer ; but from the con-
necting passages of the former to the cells of the
latter ; so that the cells of each zone alternate in
position with those of the zones that are internal
and external to it. The radial passages from the
outermost annulus make their way at once to
the margin, where they terminate, forming the
* pores ' which (as already mentioned) are to be
seen on its exterior. The central nucleus, when
rendered sufficiently transparent (by previous pre-
paration), is found to consist of a central cell {v\
usually somewhat pear-shaped, that communicates
by a narrow passage mth a much larger circum-
ambient cell (tt), which nearly surrounds it, and
which sends off a variable number of radiating

nnizopODA.

19

passages towards the cells of the first zone, which
forms a complete ring round the nucleus."

If the animal of Orbitolltes be decalcified by

Fig. 4.

Structure of Orbitolites complanatus: — a, simple disk of
Orbitolites, laid open to show its interior ; ;', central cell; v, cir-
cumambient shell, surrounded by concentric zones of cells,
connected with each other by annular and radiating passages ; —
b, portions of sarcode body of the same, showing <r, <r, <r, seg-
ments of sarcode contained in the ovate cells ; X, A, their an-
nular, and p^ p, p, their radial stolons; — c, peculiar reproduc-
tive (?) bodies ; o, gemmule, embedded in sarcode substance ;
j8, the same, undergoing fission ; 7, another gemmule, found in
one of the superficial cells.

C 2

20 EHIZOPODA.

maceration in dilute acid, the above arrangement
will be rendered still more evident {fig. 4, h).

For the contents of the ovate cells are seen to
consist of segments of sarcode (cr, a, a), from which
stolons are prolonged into the interior of both the
radial and annular passages (p, p, p, and X, X).
Each of the concentric zones of segments is, in
all probability, produced by gemmation from the
zone immediately ^^^thin it, the segments of the
innermost zone having been oi'ic^inallv budded off
by extensions of the sarcode body contained in
the circumambient cell, which, again, in its turn,
is connected by means of a narrow stolon with the
pear-shaped mass of the same substance occupying
the interior of the central cell. There can be
also but little doubt that, in the living animal, the
radial stolons of sarcode which proceed from the
outermost annulus are enabled to send forth pseu-
dopodia through the marginal pores, the latter
being the only external apertures which the shell
of the Orbitolite possesses ; and analogy would
suggest that these pseud opodia ma}^ not only
serve for the prehension of food, but may also, by
the coalescence of several round the margin of the
shell, give rise to the deposition of successive
layers of calcareous matter.

Such is the ordinary structure of Orbitolite.
But the same form is sometimes met with un-
der a much more complicated type, in which
the thickness of the entire shell is considerably
increased, and the marginal pores are seen to be
arranged in several rows, placed one above another.
Here the superficial cells, which in the simple
type are either round or oval, become nearly
rectilinear, having their long diameters placed at

EHIZOPODA. 21

ricjlit ano-les to the centre of the disk. Each of
the seofments of sarcode contained in these oblonor
chambers communicates by means of a double
footstalk with a pair of circular stolons, a con-
centric series of which lie beneath both the
upper and lower surfaces of the shell. These two
sets of stolons are connected with one another by
means of linear bands of sarcode, enclosed in
columnar chambers which run through the inter-
mediate thickness of the disk. Each of these
linear bands sends forth a double series of sarcode
threads, which serve to bring it into connection
mth a pair of the columns belonging to the zone
on its interior, those of the outermost zone having
probably the power of protruding pseudopodia
through the numerous rows of marginal apertures.
The texture of the shell is also deserving of
notice. In Gvomia and a few other forms it is
somewhat membranous, whilst in Proteonina it is
arenaceous. These, however, are exceptional in-
stances, since in the greater number of Foramiinl-
fera the shell is eminently calcareous, presenting
various degrees of consistence. In Lagena it is
hyaline, but in Miliolina and its allies it becomes
unusually opaque, so as nearly to resemble white
porcelain. In newly formed segments, the shell
is usually deficient in thickness.

TO. Tee^ss^leal Terms. — For the better de-
scription of the multilocular Rhizopods certain
technical terms have been proposed. Thus the
several chambers of which the shell consists have
received the name of segments, that from which
all the others originate by a process of gemma-
tion being known as the primordial, whilst that

c 3

22 RHIZOPODA.

which is last formed is termed the ultimate seg-
ment. Each of the segments, viewed externally,
is said to have two margins, the anterior, which is
nearest the ultimate segment, and the posterior,
which is nearest the primordial one. The parti-
tions which separate the contiguous segments
from one another are termed septa, each of which
is perforated by one or more septal apertures, and
in most cases indicated externally by a ridge or
depression, called the septal line. The superficial
area of each septum, corresponding with the en-
tire breadth of that portion of the shell where it
occurs, has been designated the septal plane.

In the nautiloid forms the term spiral suture
is employed to denote the line by which each
convolution is separated from that on either side
of it. Here the entire shell is said to have two
lateral surfaces, and a peripheral margin. The
shape of the latter, which varies considerably in
different forms, determines also that of the septal
planes. Each of these last forms three angles,
the peripheral and the two umbilical angles, the
latter being so termed because " directed towards
the centre of each lateral surface occupied by the
primordial segment, where there is usually a de-
pression or unibilicus.^^ Each of the segments
also has three margins, an anterior, a posterior,
and a peripheral. It has likewise two angles, an
anterior umbilical and a posterior umbilical.

In the trochoid shells the surface on which the
primordial segment appears is termed the " poste-
rior," while the opposite extremity is known as the
inferior, latei^al surface.

Among the straight types, such as Nodosaria,
the term " lateral aspect " is applied to the shell.

RHIZOPODA. 23

when seen in its ordinary position, its anterior
aspect being presented to our view when we look
down from above on the septal plane of its ulti-
mate segment. In Lingulina and other com-
pressed forms, the sides of the shell, when viewed
edgeways, are said to present their " periphero-
hieraV^ aspect, the same term being also applied
to the Nautiloid shells, when viewed in the di-
rection of their peripheral margins.

1 1. Distribution of Foraminifera in space.

— By far the greater number of Foraminifera are
marine. They are found in most seas, preferring,
however, those of tropical and southern climes,
where an increase may be observed, not merely in
the number and variety of the specimens, but
likewise in the size which several of the latter
attain. Many of the Foraminifera have been
dredged from considerable depths, some in a
a living state ; and there is reason to believe that
extensive deposits of their shells, associated with
those of other minute organisms, are in process of
formation on several parts of the existing sea
bottom, more especially in the North Atlantic,
the Eastern Mediterranean, and the Australian
Seas.

Among the more widely distributed animals of
the present group may be especially mentioned
Orbulina and Glohigerina, both of which forms
may be regarded as almost cosmopolitan.

Specimens of Foraminifera may be obtained for
examination from the shakings of dried Sponges,
or even from the sand on most parts of the sea
coast : but, should they be required for observation
of the contained animal, they must be dredged for

C 4

24 EHIZOPODA.

this purpose from suitable localities, or picked,
with the aid of a lens, from the fronds of living
sea weeds, over the sm'face of which they may be
observed to crawl by means of then* pseudopodia.

12. Distribution of F«ra?5ii«irera in tini<».

— Eemains of Foramlnifera have been proved to
exist in most of the stratified rocks, from the
Silurian to the Tertiary inclusive ; many of the
forms found in the older formations being nearly,
if not absolutely, identical with those which occur
in the seas of our own epoch. But the insufficient
and superficial manner in which the " genera " and
" species " of these animals have too frequently
been characterised, has considerably deducted from
the value of those facts from which conclusions
miofht otherwise be deduced with reference to their
distribution.

Amonof Paleozoic strata remains of these ani-
mals have been found to occur in both the Silurian
and Carboniferous series. The green grains which
lie scattered through the Lower Silurian sand-
stones of the neighbourhood of St. Petersburg!!
have been shown by Ehrenberg to contain in their
interior siliceous casts of Foraminiferous shells,
some of which are referrible to such existing forms
as Guttulina, Rotalia, and Textularia. The two
last mentioned of these have been likewise de-
tected in the Carboniferous limestone, certain beds
of which, found in Russia and the United States,
are composed, for the most part, of the shells of
Fusulina, a form which would seem to be exclu-
sively confined to this deposit.

Among secondary rocks, Foraminifera prevail
in both the oolite and chalk, being, however, more

EHIZOPODA. 25

numerous in the latter, extensive beds of which
are in many districts made up of Httle else than
the shells of Rotalia, Spirulina, and Textidaria.

But it is in the formations of the Tertiary
period that this group may be said to have at-
tained its greatest development. It is here we
first meet with the widely distributed Kumviulites,
whose size, compared with that of any Forami-
nlfera which have preceded them, must be consi-
dered as gigantic. They are chiefly characteristic
of the Middle Eocene ; and it has been proposed
by some geologists to divide this formation into
three sections, each being distinguished by a se-
parate form of Nummulite. The extent to which
some of these strata prevail has been thus indi-
cated by Sir Charles Lyell.

" The Nummulitic formation, with its charac-
teristic fossils, plays a far more conspicuous part
than any other tertiary group in the solid frame-
work of the earth's crust, whether in Europe,
Asia, or Africa. It often attains a thickness of
many thousand feet, and extends from the Alps to
the Carpathians, and is in full force in the North
of Africa, as, for example, in Algeria or Morocco.
It has also been traced from Egypt, where it was
largely quarried of old for the building of the
Pyramids, into Asia Minor, and across Persia, by
Bagdad, to the mouths of the Indus. It occurs
not only in Cutch, but in the mountain ranges
which separate Scinde from Persia, and which
form the passes leading to Caboul; and it has
been followed still farther eastward into India, as
far as Eastern Bengal and the frontiers of China."

It has been shown by Dr. Carpenter that the
Nummulitic limestone of some districts contains

26 EHIZOPODA.

the remains, not of Numrmdites proper, but rather
of a form which, though resembling it closely in
external appearance, is in internal structure very
dissimilar. For this form he has proposed the
name of Orbitoides. The same observer has also
given it as his opinion, that between the existing
Nonionina and the true fossil Numifnulites there
exists no important difference of structure.

13. Size of Rhizopoda. — All the Amcehea
are microscopic, being seldom known to exceed
•02 of an inch in diameter. The Foraminifera are
somewhat larger, the linear dimensions of the
recent British species (for example) varying from
•005 to '050 of an inch. But among the tropical
and extinct forms of the group we meet with
many whose size is much more considerable ;
NuTiimidites being frequently at least three inches
in circumference, while specimens of Cyclocly-
peus have been met with which have been found to
reach 2*25 inches in diameter.

14. Development of Rliizopoda. — Almost
nothing is kno\\Ti of the development of the Rhi-
zopoda. Difflugia and Actinophrys have been
observed to undergo multiplication by fission (i. e.
the separation of the body into two parts), and the
last-mentioned form also propagates itself by a
peculiar method which presents some slight ana-
logy to the " conjugating process " among the
lower Algse. In the body of Orbitolites Dr. Car-
penter has observed the sarcode to be " broken up
(as it were) into little spherules," and these he sup-
poses are probably " gemmules " destined for ex-
pulsion through the marginal pores. He has also

EHIZOFODA. 27

detected, imbedded in the sarcode, certain other
bodies {fig. 4, c), which may be either " gem-
mules in a later stage or possibly true ova (?)."
These exhibit various stages of binary division,
and always present a deep red colour. But their
exit, and subsequent development, have hitherto
escaped observation.

28

POLTCTSTINa

CHAPTER III.

POLYCTSTIXA.
I. Nature. — 2. Distribution.

I. Ifatwre. — The name Polycystina was first
given by Ehrenberg to a gi"oup of minute shell-
bearing organisms, apparently allied to the Fora-
minifera. They are usually of smaller size than
the latter, from which also they differ in the nature
of their shelly investment, the composition of
which is siliceous. These shells are remarkable
for the great beauty and variety of their forms.

Fig. 5.

Polycystina

a, Podocyrtis Schomhurgkii ; b, Haliomma
Humboldtii.

and the peculiar appearance of the spine-like
projections with which they are frequently fur-

POLTCYSTIXA. 29

nislied {fig. 5). The contained animal consists
of an olive brown sarcode substance capable of
protruding pseudopodia through the numerous
foramina with which the shell is perforated. In
those forms which have been most carefully exa-
mined, the sarcode body, which is divided into four
equal lobes, does not fill the entire cavity of the
shell, but would seem to be wholly confined to the
upper portion of the latter. Of the true nature of
these creatm-es, much has yet to be learned.

2. IJisti-!!)'!i*i<i» s. — The Polycystina are very
widely distributed. Their shells, mingled with
those of Foraiiiinifera and Diatomacece, have been
ascertained to form part of the extensive organic
deposit which is now being formed over a portion
of the bed of the North Atlantic. They have been
found also in the Mediterranean and various other
parts of the existing ocean. They appear, how-
ever, to have been even more numerous at former
periods, their remains having been already de-
tected in both the secondary and tertiary forma-
tions. Nearly 300 apparently distinct forms of
these animals have been discovered by Ehrenberg,
in a tertiary deposit which occurs abundantly
throughout an extensive district of the island of
Barbadoes.

30 SPONGIDJ!.

CHAPTER IV.

SPOXGID^.

I. Animal nature. — 2. Form and Size. — 3. Skeleton — 4. Aqui-
ferous system. — 5. Reparative powers. — 6. Spicula. — 7. Classi-
fication. — 8. Structure of Tethya. — 9. Development. — 10. Dis-
tribution. — II. Affinity to Foraminifera.

I. Animal natare. — If the animal nature of
the Rhizopoda be admitted, that of the Sponges
can no longer be regarded as doubtful. For a
Sponge consists of a soft gelatinous substance,
supported by an internal framework or skeleton,
the whole being usually strengthened by the
addition of calcareous or siliceous ' spicula.' The
soft gelatinous flesh is found, on examination, to
be composed of an aggregation of amoebiform
bodies, and must be considered as constituting the
essential part of the animal, since in some Sponges
the skeleton is altogether absent, whilst in others
the mineral spicula are replaced by particles of
sand.

In Grantia (one of the marine Sponges) the
amoeba-like particles are furnished with long
filamentary appendages, which have received the
name of ' cilia ' (^fig» 6, e). To these peculiar
organs, which now for the first time make their
appearance in the animal kingdom, we shall here-
after more fully allude (p. QQ\ Ciliated parti-
cles have likewise been noticed in the gelatinous
substance of the fresh-water SjDonges {SiDongilld) ;
but here they are not present at all times of the
year, having been observed to disappear on the
approach of mnter, during which season the body

SPONGID^.

31

of Spongilla solely consists of amorphous non-
ciliated amcebiform bodies. But it is right to
mention that the structure of these last is as-
serted by Lieberkiihn to be not quite so simple
as some naturalists have supposed.

Fig. 6.

Structure of Grantia, &c. : — a, b, c, siliceous spicula of Hali-
chondria ; d, portion of Grantia compressa, showing arrange-
ment of triradiate (calcareous) spicula ; e, smaller portion oS
the same (more highly magnified), showing ciliated amoebiform
particles.

2. Form and l§ize. — The various kinds of
Sponges present themselves to our notice under
every possible diversity of size and outward
configuration. Some form flattened incrustations
investing the surfaces of rocks, shells, and various
submarine objects ; others occur as dense compact
masses, often of considerable dimensions; others,
again, are erect, cup-shaped ; while not a few
assume the aspect of branching arborescent struc-

32 SPONGID^.

tures. In size, the Sponges far exceed all other
Protozoa ; aggregate masses of these animals being
sometimes met with, chiefly on the shores of tro-
pical seas, which cover surfaces of many yards in
extent.

3. Skeleton. — The skeleton or framework of
the Sponge, which is best seen in dried specimens,
is usually composed of a number of horny fibres,
anastomosing one with another in such a manner as
to form an irregular though intricate network. In
some sponges, e. g. Gh^antia, this fibrous network
is altogether wanting. In the Sponges of com-
merce it attains an unwonted degree of softness
and elasticity, which qualities, combined with the
comparative paucity of their spicula, give to these
substances their chief value in a commercial
point of \dew. In certain tropical Sponges, on the
other hand, it is found to be entirely made up of
siliceous particles ; these, however, still presenting
that characteristic reticulated arrangement which
may be regarded as essentially distinguishing the
' fibre ' from all the other structures which together
make up the body of the Sponge.

4. Aquiferous System. — With the porous
aspect of ordinary Sponges most persons are
familiar. On more careful examination it will be
seen that these pores are of two kinds: i. the
larger pores, which are comparatively few in num-
ber and frequently elevated on slight prominences ;
and 2. the smaller pores, which are much more
numerous, crowding the entire surface of the
Sponge so as to occupy the interspaces between
the larger apertures. The latter are properly de-

SPONGID^. 33

nominated ^oscula,' the smaller orifices being spe-
cially distinguished as the * pores.'

On cutting open the Sponges, the oscula and
pores are seen to be connected each with its proper
system of ^ canals.' What are termed the ' ex-
current ' canals proceed immediately from the os-
cula, and, after forming a somewhat complicated
network within the outer layer of the Sponge,
finally communicate with another system of * in-
current' canals, which, in their turn, terminate
in the Spores.' Both of these sets of canals
are produced by the peculiar arrangement of the
horny fibres which compose the skeleton, and
in the living animal are invested on all sides
by a coating of the glairy gelatinous sarcode.

If a fragment of living Sponge be placed, in a
watch-glass, on the stage of a microscope and ex-
amined with a low magnifying power, a curious
spectacle will, under favourable circumstances,
come into view. Currents Tvill be seen to issue
rapidly from the oscula, whilst at the same time
water is being continually absorbed by the pores.
In this manner a sort of circulation is maintained
within the two systems of canals which connect
the oscula and pores with one another. The
currents are rendered more readily observable, by
diffusing finely powdered indigo or carmine in the
water containing the specimens under examina-
tion.

When the foregoing phenomena were first
noticed (in 1827) by ^^' Cri'ant, they excited much
attention among naturalists, though for a long
time afterwards the mechanism by which they
were effected, remained altogether undiscovered.
More recently the subject has been investigated

D

34 SPONGID.E.

anew by Dr. Bowerbank, from whose observations,
made, for the most part, on the common fresh-
water Sponge, the follo\ving conclusions seem dedu-
cible, viz. : —

1. That the circulatory action is, in all probabi-

lity, due to the presence of vibratile cilia.

2. That these cilia (if present) are situated, not

around the oscula or pores, but rather within
the larger excurrent canals which run im-
mediately beneath what may be termed the
" dermal membrane " of the Sponge.

3. That the circulatory action is, to a certain

extent, periodical, continuing for a sufficient
length of time to enable nutrient particles
to be conveyed to all parts of the interior of
the Sponge, after which it becomes languid
for a while, to be again resumed, when its
performance is called for to supply the ne-
cessities of the organism.

And further, it has been proved,

4. That the living animal possesses the power

of opening and closing its oscula at plea-
sure ;

5. That the several oscula may act more or less

independently of one another ; and

6. That new oscula may be formed, if required,

any^vhere in the course of the larger excurrent
canals.

It is obvious that the above currents may be
employed, not merely in the conveyance of food,
but likewise in the removal of effete matter.
They contribute, moreover, to the general aeration
of the entire animal, presenting us, it may be said,

SPONGID.E. 35

with the first indication of a respiratory apparatus.
It would seem also that the nutrient matters con-
veyed by the currents to the interior of the canals
are there assimilated by the sarcode substance
lining the latter, much in the same way that par
tides of food are approiDriated by the gelatinous
processes of Actinophrys or A'nweba,

5. Meparative powers. — The reparative
powers which many Sponges possess are by no
means the least remarkable of their vital pheno-
mena. If the substance of the Sponge sustain in-
jury by incision or otherwise, the wounded sur-
faces will be found, in the majority of instances,
after a short time, to have completely healed. It
has also been proved that separate fragments be-
longing to the same species of Sponge, if placed in
contact and allowed to remain undisturbed, will
often, within a few hours, unite together, so as to
form a single specimen ; and it has been further
ascertained that the process of adhesion is in no
wise interrupted by suffering the water to drain
away from the specimens which are made the sub-
ject of experiment.

6. Spietila. — The spicula or mineral bodies,
which are found in the majority of Sponges, vary
considerably both in form and size {figs, 6 and 7).
They occur throughout all the various structures
of the animal, each of whose parts is stated by
Dr. Bowerbank to contain its appropriate forms
of these bodies ; one kind of spicules being found
in the skeleton, another in the sarcode substance,
whilst others, which project beyond the surface of
the Sponge, are presumed to be of use in defending

D 2

36 SPOXGID.E.

their possessor from the attacks of other animals.
Those which occur in the sarcode are usually of
the kind which have been denominated ' stellate,'
many of them presenting a curious complexity of
structure. Other spicules, whose forms are no less
peculiar, are found in connection with the so-called
' gemmules ' and similai* reproductive bodies : thus
in Spongilla, each of the spicula by which the
" seed-like body " is surrounded presents the ap-
pearance of a pair of toothed wheels united to-
gether by an axle {fig. 8).

The composition of the spicula is, in most cases,
siliceous, but in Gvant'ia and a few other forms
they are found to be composed of carbonate of
lime.

It is evident from the peculiarity and constancy
of the forms which spicula assume, and from the
total absence of anything which can be compared
to a crystalline structure, that they are to be re-
garded as true organic deposits, resulting, it would
seem, from the vital endowment of sec^ments of
the sarcode body especially set apart for their se-
cretion.

7. Clasf^ilication. — We possess no good clas-
sification of the Sponges, the several " genera " and
" species " into which this group of animals is
usually divided having been far too insufficiently
examined to permit any arrangement of them
w^hich has hitherto been proposed to be regarded
as aught else than temporary. We shall therefore
select as an example of this section of the Proto-
zoa the form denominated Tethya, not that it is
to be regarded as its most typical representative,
but rather because its structure has been more

SPONGID.E. 37

fully investigated than that of most other members
of the group.

8. §triieture of Tethya. — From the obser-
vations of Prof. Huxley it would appear that this
Sponge consists essentially of three distinct struc-
tures, viz. : —

1. A central, whitish, spherical substance {fig. 7,

6, X) ; composed of a granular mass, asso-
ciated with numerous cylindrical spicula.

2. A yellowish red intermediate portion {fig. 7,

h, 13) ; composed of a granular uniting sub-
stance in which ova and stellate spicula (a, k)
are embedded.

3. A deep red cortical substance (6, a); con-

sisting of two zones, which merge insensibly
into one another. Of these, the inner is
composed of closely interwoven bimdles of a
filjrous tissue, and contains only a small num-
ber of stellate spicules, whilst the outer zone
is dense, granular, " containing great num-
bers of crystalline spheres beset with short
conical spikes."

The rod-like spicula which occur in the central
substance are usually so arranged as to form an
irregular network, becoming aggregated into bun-
dles as they approach the intermediate substance.
The several spicula contained in these bundles are
at first nearly parallel to one another, bub they
gradually diverge as they radiate through the
latter, terminating at length, in the cortical layer,
beyond which a small number not unfrequently
project. Numerous long solitary rods, in addition
to the bundles, also radiate through the interme-

T> 3

38

SPONGID^.

diate substance. The longitudinal axis of each of
the rods is traversed by a very narrow canal.

To return to the intermediate substance. Its
granular mass is found to be altogether made up
of small circular cells (a, (o), "and of sperma-
tozoa in every stage of development from those
cells. The cell throws out a long filament which
becomes the tail of the spermatozoon, and becoming
longer and pointed forms, itself, the head. The
perfect spermatozoa have long, pointed, somewhat
triangular heads about -3-0^-0 of an inch in diameter,
with truncated bases, from which a very long fili-
form tail proceeds."

" The ova (a, o) are of various sizes. The largest
are oval and about 3^^ of an inch in long diameter.

Fig. 7.

\

^g^^^^ <>

Structure of Tethta : — a, portion of the intermediate sub-
stance of Tethya (magnified), showing 0, ova embedded in sper-
matic mass («), together with stellate bodies (k); — b, section of
Tethya (nat. size), showing A, central portion, iS, intermediate
substance, a, cortical layer, 5, canals.

They have a very distinct vitellary membrane,
which contains an opaque coarsely granular yolk.

, 55

SPONGID^.

39

In the centre of each, surrounded by a clear space
may be noticed the * germinal vesicle/ and mthin
the latter a minute * germinal spot ' may sometimes
he seen.

9. Ilevelopment. — The development of the
Sponges is effected,

a. by ova and spermatozoa;

b. by various other bodies, the true nature of

which is not yet sufficiently determined.

a. True reproduction has hitherto been proved
to take place in Tethya alone, although from
analogy, there can be little doubt that it must

Fig. 8.

Structure of seed-like body of Spongilla : — a, one of the seed-
like bodies of Spongilla Meyeni, shown in magnified section ; b,
one of its spicula seen in profile ; c, the same, viewed endways ;
d, germs of cells of a (very much magnified) ; e, one of the cells
cf a, containing germs ; /, portion of coriaceous membrane of
a, showing hexagonal divisions and transparent centres.

also occur in most other forms of the group. In
the fresh-water Sponges small moving corpuscles,

D 4

40 SPONGID.E.

similar to the spermatozoa of Tethya have been
recently detected by Lieberkiihn.

6. Carter has described certain '* seed-like
bodies " {fig. 8, a) which are found embedded ia
the gelatinous substance of Spongilla. Each of
these consists of a round or ovoid coriaceous cap-
sule, the sm'face of which when magnified, pre-
sents a hexagonally tessellated appearance (/), and
is surrounded by a zone of the peculiar asteroid
spicula (b, c) to which we have already referred
(p. 36), these being embedded in a coating of gela-
tinous matter. Within the capsule are numerous,
transparent, spherical "ovi-bearing cells" con-
taining granules and germs in their interior {d, e),
and surrounded by a cortical layer of peculiar
nucleated cells. MTien arrived at matmity the
contents of the seed-like body escape through the
hilum or aperture with which it is provided,
" under the form of a gelatinous mass, in which
the ovi-bearing cells and their contents appear to
be embedded entire." Next, spicula are developed
and with them a delicate pellicle or "investing
membrane " which would seem to be formed from
the nucleated cells of the cortical layer. This
becomes separated by an interval or " cavity ""
from the " parenchyma " or gelatinous substance
enclosing the ovi-bearing cells. Apertures sub-
sequently originate in the investing membrane,
whilst at the same time a canal system is being
formed in the parenchyma ; and, finally, the ovi-
bearing cells are developed into a number of
stomachal or " ampullaceous " sacs, which open
into the incm-rent canals.

From the investigations of Lieberkiihn it would
appear that the propagation of Spongilla is some-

SPONGID^. 41

times effected by peculiar bodies to which the
name of " swarm spores " has been given. These
were oval in form ; more pointed at one end than
at the other and consisted of three distinct sub-
stances; viz. I, an epithelial cellular envelope;
2, a structureless cortical layer ; and 3, an interior
spheroidal medullary portion. The latter is re-
solvable into an exterior mucoid layer, containing
a variable number of " germ granules," embedded
in an albuminous substance and associated with
numerous minute siliceous spicula. The swarm
spores were actively locomotive, swimming ra-
pidly about by means of the cilia which were dis-
posed in a regular manner over the entire surface
of their bodies. After leading a somewhat restless
existence for one or two days they sunk to the
bottom of the vessel wherein they were confined,
to which they soon after began to adhere. The
greater number decayed ; a few, however, were
observed to expand into a delicate layer consisting
of a gelatinous substance in which minute siliceous
needles were embedded, and at length, on the
20th day, the characteristic Sponge structures
made their appearance.

In addition to the germ-granules contained in
the swarm spores, spherical aggregations of the
same bodies, in a free condition, were not unfre-
quently met with. They were found in all parts of
Spongilla, being especially abundant at the base
or attached portion of the mass.

With regard to the natiu:e of the above swarm
spores, and the relation which exists between them
and the seed-like bodies, much has yet to be
learned. Carter asserts that they are merely ciliated
forms of the latter, a statement which, however

^

42 SPONGID^.

probable, must for the present be considered as
un proven.

In the interior of the canals of some marine
Sponges minute bud-like extensions of the sarcode
substance may readily be observed at certain sea-
sons of the year, and these, which are provided
with cilia, detach themselves from the body of the
parent, and probably, at length becoming fixed,
give rise to new Sponge formations. But it may
be questioned whether these bodies have not been,
in many cases, confounded mth true ciliated
swarm spores, similar to those which are found in
Spongilla.

10. distribution The distribution of the

Sponges may be compared, in many respects, to
that of the Fovaminifera. Like them they are
almost exclusively marine, are found in most
climates, but occur most abundantly, are more
varied in form, and luxuriant in growth, on the
shores of the warmer regions of the globe. Like
them also they have been found in most of the
geological epochs from the Silurian period to the
present. The Sponges of the chalk have more
especially attracted attention, the well known flint
nodules of that formation, in many cases, owing
their peculiar form to the presence of the extinct
remains of these animals. Several fossil Spongidse
have been figured and described of which PalcBO-
spongia is said to be peculiar to the Lower Silurian ;
Actinospongia, Goniosjjongia, and Perispongia
to the oolite ; and Hemispongia, Thalamospjon-
gia, Meandrospongia, Retispongia, Ccelopty-
climm, PleuTostoma, Turonia, with many others,
to the chalk. The curious genus Cliona, which

SPONGID.E. 43

possesses the remarkable power of excavating bur-
rows for itself in shells and other calcareous
bodies, is found in most of the secondary and
tertiary formations, and is sufficiently abundant
along the shores of the existing ocean. Since,
however, we are still by no means certain as to
what constitutes a genus among recent Sponges, it
is evident that even greater difficulties must at-
tend our investigations among extinct forms, and
hence, any tabular arrangement showing the
successive appearance and relative distribution of
these *^ genera '' seems to us, at present, premature.

II. AflSaaity to Foraisiiaiifera The nature

of the relationship between the Sponges and
amoebiform Ehizopods has been already alluded
to. Eecently, Dr. J. E. Gray has described, under
the names of Carpenteria and Dujardinia, two
remarkable attached forms of Protozoa, present-
ing characters intermediate between those of the
Spongidce and Foramninifera. Both of these are
furnished with conical calcareous shells, composed
of an aggregation of elongated chambers disposed
in a spiral, the orifice of the last-formed chamber
being placed at the apex of the entire shell. In
Carpenteria, the interior of the chambers " is
filled with a fleshy sponge-like body, strengthened
by numerous minute, simple, pin-shaped and
fusiform smooth spicula placed in bundles." In
both of these organisms the entire shell is pierced
with very many, minute, circular perforations.

44 THALASSICOLLID.E.

CHAPTER V.

THALASSICOLLID^.
I. External characters. — 2. Organisation. — 3. Acanthometrse.

1. External characters. — The group of
TJialassicollidce includes certain gelatinous marine
animals which, though abundant in most seas,
would appear to have remained altogether unno-
ticed until the year 1851 when Mr. Huxley first
directed the attention of naturalists to the pecu-
liarities of structure which they present. They
can scarcely be said to possess any determinate
form, and seem to be destitute of the power of vo-
luntary motion, being usually found floating near
the surface of the water. In size they vary from
an inch downwards.

2. Orgasaisatioii. — Sphoirozoum 'punctatum^
one of the most abundant of these animals,
presents in many cases a somewhat ovate body
constricted in the centre {fig. 9, ci), and is found
to consist of a transparent, colourless, gelatinous
substance, destitute of structure, surrounding a
large internal cavity. Enclosed in the gelatinous
mass are a number of isolated, minute, "cellae-
form bodies " (e), each of which consists of an
external membrane filled with granular contents,
mthin which a " clear fatty-looking " nucleus may
be observed.

The gelatinous mass frequently contains mi-
nute, yellow, spherical cells, these being either
irregularly diffused through its substance or
gi'ouped around each of the cellseform bodies.

THALASSICOLLID^

45

The cellseform bodies are often surrounded
by peculiar cylindrical spicula, terminating at
both extremities in three or four conical rays,
beset on either side with minute spine-like pro-
cesses.

Fig. 9,

Structure of Thalassicollid;e : — a, Sphcerozoum pimctafum
(nat. size) ; b, variety of the same ; c, ThalassicoUa nucleata ;
d. CoUosphcera Huxhy'i; e, portion of a (magnified), showing
two of the celloeform bodies with their coloured vesicles, nuclei,
and spicula.

In some specimens the central cavity is re-
placed by an aggregation of large vacuolar
spaces (6).

ThalassicoUa proper is more constant in form
than the preceding, and is destitute of cellaeform
bodies (c). It contains, however, the coloured vesi-
cles above referred to ; these, associated ^vith vacu-
olar spaces and very many minute dark gi-anules.

46 THALASSICOLLID.E.

being aggregated round a blackish body placed in
the centre of the spherical mass. The dark cen-
tral body is found on examination to consist of
a strong elastic membrane, enclosing a pale
nucleus-like vesicle, embedded in a somewhat
peculiar granular substance. Numerous slender
branching ''fibrils" radiate through the gelati-
nous body from the interior of the dark central

mass.

In CollosphcB^^a the spicules are absent, but the
entire animal is enclosed in a transpai'ent, reticu-
lated, very brittle shell (d).

From the preceding account it will be evident
that the Thalassicollidce differ essentially from the
other groups of Astomatous Protozoa, though they
at the same time present remarkable affinities to
more than one of these. Of their animal nature
no doubt can be entertained, notwithstanding the
assertion made by some that " they are referrible
rather to the Diatomacese," whilst others have de-
signated them " agglomerations of organised ra-
"phides, as it were, raised to the state of inde-
pendent beings."

3. Acantliometree. — The curious Acantho-
metrcB of J. Miiller are closely allied to the pre-
ceding. Their peculiar, siliceous, radiating spines,
which meet in the centre of the gelatinous body
and project in most cases considerably beyond
its surface, will sufficiently serve to distinguish
them {fig. lo). Like the ThalassicollidcB, the
AcantJiometrcB are marine, and destitute of loco-
motive power. In size they are more minute.
It was proposed by Miiller to unite these animals

THALASSICOLLID-E.

47

Fiq T o.

ACANTHOMETRA LANCEOLATA.

together with the Polycystina and Thalassicollidce
into a group by themselves named Rliizojpodia
radiolaria. This arrangement is indicated in the
accompanying table.

48 TnALASSICOLLID.E. v,^

TABLE
SHOWING MULLER'S ARRANGEMENT OF

THE THALASSICOLLID^, POLYCYSTINA,
AND ACANTHOMETE^.

RHIZOPODA RADIOLARIA.

A. RADIOLARIA SOLITARIA.

(^Sinrjle.)

1. Thalassleollina.

(Animal naked : with or without siliceous spicula.)

2. Polycystisaa.

(Animal enclosed in a siliceous, reticulated, shelly covering. )

3. Acanthometra.

(Animal naked: with siliceous radiating spines.)

B. RADIOLARIA POLYZOA.

(Aggregated.)

1. l§pb8erozoiiiidae.

(Animal naked : with or without siliceous spicula.)

S. Collospliaeridae.

(Animal enclosed in a siliceous reticulated covering.)

GEEGAEI^'ID^. 49

CHAPTER VI.

GREGAPJNID^.

1. Habit. — 2 Form and Structure. — 3. Development. — 4. Classi-
fication. — 5. Psorospermi^e.

1. Habit. — Dufour was the first to designate
under the name of GregavincB a group of micro-
scopic organisms which differ remarkably in habit
from the preceding Protozoa, since they have
hitherto been only known to occur as parasites
wdthin the bodies of other animals, more especially
those belonging to the sub-kingdom Annulosa.

2. Forsii a;id ^trtic*l?ire. — The form of the
body varies, being, in most cases, more or less
ovate. In many Gregarinidce it is marked by
clefts or strictures which, with their corresponding
internal septa, divide it into two or more segments
{Jig. 11). In some, a sort of process projects
from one end of the body, and this is frequently
furnished at its extremity with a number of re-
flexed booklets, by means of which it is supposed
that these animals are enabled to attach them-
selves more firmly to those surfaces whereon they
are usually found (c^).

Anatomically, the Gregarinidce are found to
consist of a transparent membrane enclosing a
mass of granular contents, in the interior of which
a nucleus, surrounded by a well defined clear
space, may in most cases be observed (c, d, f ).

The Gregarinidce are colourless, and would
appear to possess a limited amount of locomotive
power.

E

50

GREGAEINID.E.

3. Development. — These animals have been
observed to propagate by a peculiar method, to
which the term " conjugating process " has been,
it would seem, somewhat hastily and erroneously
applied. Two Gregarince come into contact and a
cyst or capsule soon forms around them both.

Fig. II.

GREGARiNiE and PsoRC'SPERjii.E : — a, cyst of Gregarina sce-
nuridis, with two cells, containing in their interior a number of
pseudonaviculre ; b, Gregarina Sipunculi, with two enclosed
cells ; c, two Gregarince scenuridis, adhering together by their
ends; d, Gregarina Sieholdii; e, peculiar pseudonavicula (?)
from abdominal cavity of Sipunculus uudus ; /, younger
stage of a ; g, various PsorospermicB.

Next, certain globular vesicles are produced in the
interior of the C3''st, and these become ultimately
metamorphosed into peculiar bodies which have
received the name of *' pseud onaviculie" (a, e, /).

GEEGARIXID.E. 51

The partition by which the two Gregarince were
at first separated meanwhile disappears, the cyst
bursts, and the pseudonaviculae escaping therefrom
burst in their turn, and give rise to amoebiform
bodies which at length develope themselves into
young Gregarinidce, But the coalescence of two
Gregarinidce is by no means a necessary prelimi-
nary to the formation of pseudonaviculae, since
these are sometimes observed to occur within the
bodies of single animals.

4. Classification. — The Gregarinidce have
been divided by Stein into three sections, viz. : —

1. MonocystidecB. — Simple Grregarinidse without

constrictions or internal septa.

2. Gregarmarice. — Gregarinidse with the body

divided into two portions.

3. Didimophydce. — Gregarinidse with the body

divided into three parts, as if resulting fi-om
the adhesion of two individuals, one from each
of the preceding sections.

This, however, is merely an arbitrary division,
and, if not erroneous, is certainly premature.

By some the Gregarinidce have been regarded
as vegetable forms ; by others, as larval stages of
various Annuloida, Neither of these opinions has
been supported by proofs, and, upon the whole, it
seems desirable, for the present at least, to view
these organisms as adult members of the sub-
kingdom Protozoa,

5. Psorosperniiee. — The Psorosperonice are
exceedingly minute parasitic creatures, occurring
in great numbers both on and within the bodies
of fishes. In form they are ovate, hemispherical,

E 2

52 GEEGARI^'ID^

or depressed, and are frequently provided with a
peculiar fish-like tm\ {Jig. 11, g). They consist
of a somewhat tough external membrane, within
which are two or more oblong vesicles, usuallji
situated near the anterior extremity of the body.
In addition to these a globular mass of organisable
matter may often be observed. Lieberkiihn has
shown that, under certain circumstances, the Pso-
rospermiicB may burst, when the globular mass, thus
liberated, mil be found to resemble the amcebiform
bodies resulting from the rupture of the pseudona-
viculae above referred to. Hence it is exceedingly
probable that the Psorospermice are identical with
the pseadonaviculae of true Gregarinidce.

iNFrsoKiA. 53

CHAPTER VII.

IXFUSORIA.

I. Nature of Infusoria. — 2. Example of the group : Vorticella

3. Classification. — 4. Size. — 5. Form and Structure. — 6. Diges-
tive apparatus. — 7. Contractile vesicle. — 8. Nucleus, &c. —
9. Urticating organs. — 10. Locomotive organs. — 11. Develop-
ment.— 12. Distribution. — 13. Noctiluca.

I. IVature of Isafiisoria. — If water, in con-
tact with organic matter, be exposed to the atmo-
sphere for a few days, it will probably be found to
contain, upon examination, a considerable number
and variety of living beings, whose size is such as
to render the majority of them invisible to the
unassisted eye. These minute creatures received
from the older microscopists the name of Infuso-
ria, a term having reference to their frequent oc-
currence in most animal and vegetable infusions.
Subsequently, they were investigated with great
industry by Ehrenberg, who figured and described
a vast number of " species " belonging to the
group, all of which he arranged under two leading
divisions, denominated respectively, Rotifera and
Polygastrica. But the recent observations of se-
veral eminent naturalists have, however, shown

1st, That the organisation of the Rotifera is of
a far higher nature than had been suspected
by Ehrenberg, and that the true position of
these animals is in the Annuiose sub-kinofdom*
and,

2ndly, That the Polygastrica of Ehrenberg may
be defined as a heterogeneous assemblage of

E 3

r.

4 INFUSORIA.

minute (in most cases, organised) beings,
chiefly consisting of

A. Rliizopoda;

B. Unicellular and other Algse ;

C. Embryonic forms ; and, lastly,

D. True Infusoria.

The true nature of many of the Infusoria
proper is still a disputed question.

According to Dujardin, their bodies are com-
posed of a gelatinous substance, similar to that
which we find among the Rhizopoda. By Siebold,
Meyen, Kolliker, and others, they have been re-
garded as unicellular animals ; a view of their
nature which certainly does not appear to be con-
firmed by the examination of the more highly or-
ganised forms. Agassiz, on the other hand, has
endeavoured to get rid of the entire gi'oup of In-
fusoria by assigning higher positions in the animal
kinofdom to those of its members whose non-em-
bryonic nature would seem to be fully established.

In the midst of so many conflicting opinions,
the following course has seemed to us most worthy
of adoption.

Combining the results of our ovm recent obser-
vations with those of the more elaborate inves-
tigations of Claparede, Lachmann, and others, we
shall, with some limitations, adopt the views of the
last-mentioned authors, and define the InfusoriasiS
Animals belonging to the department of Proto-
zoa, provided with a mouth and rudimentai^
digestive apparatus; their bodies usually con-
sisting of three distinct layers, the outer of vjhich
is, in most cases, furnished vjith a variable num-
ber of cilia.

INFUSORIA.

55

2. Example of the group : Yorticella.

— A good example of the true Infusoria is fur-
nished by Vorticella, a large and well-known
form, found plentifully on the roots of duckweed
and other similar situations. A group of these
elegant organisms, when placed under the micro-
scope, presents the appearance of a number of
bell-shaped vases, each of which surmounts the
extremity of a slender pedicle or stalk {fig. 12, a).

F'u.

12.

Structure of Yorticella, &c. : — a, group of Vorticella ne-
hulifera, showing at a, a Vorticella spirally contracted on its
stalk ; /3, another form, with its cilia retracted ; 7, a third form,
undergoing fissiparous division ; 5, a detached Vorticella bud,
furnished with a posterior circlet of cilia ; — h, upper portion of
Vorticella campanula (very much magnified) ; (p, commence-
ment of ciliary spiral ; tt, peristome , A, lumen of CESophagus ;
/3, bent bristle situated in the vestibulum ; 0, one of the stronger
cilia which arise in front of the mouth ; k, contractile vesicle ;
V, band-like nucleus ; j, cuticle ; ,u, contractile filament of stem
forming apical prolongation of contractile layer ; — c, diagram-
matic section of Paramecium, showing t, cuticle bearing the
cilia ; K, K, contractile vesicles contained in the parenchyma of
the body, |.

E 4

56 INFUSORIA.

If one of these vase-like bodies (b) be carefully
examined, its edge is seen to be surrounded by a
projecting rim or border, wbich has received the
name of ^ peristome ' (tt). Within the latter is
placed the ' disk/ the outer edge of which is
provided with one or more circlets of cilia (^).
The peristome itself is not fm-nished with these
appendages. The mouth is placed in a small
opening situated near the edge of the disk,
between it and the peristome. The disk, which is
separated from the peristome by an intervening
furrow, forms the upper surface of a peculiar pro-
cess termed the ' rotatory organ,' which the
animal has the power of retracting deeply into the
interior of the body, over which latter a covering
is then formed by the contraction of the peri-
stome. The cilia with which the outer edge of the
disk is furnished are arranged in a spiral line.
This spiral commences a little to the right of the
oral orifice, above which it proceeds towards
the left, and, after performing one or more revolu-
tions round the edge of the disk, descends into the
' vestibulum ' or commencement of the digestive
apparatus. In addition to the oral orifice, the
vestibulum is provided with a lateral aperture
which would appear to discharge the fimction of
an anus. Between the anus and the mouth
springs a stiff bent ' bristle ' (/S), which usually
projects beyond the edge of the peristome. From
the vestibulum a short tube called the * oesophar-
gus ' leads to a wider portion of the digestive
canal which has been termed the 'pharynx.'
The latter is fusiform in shape, being truncated at
its lower extremity, which hangs down into the in-
terior of the body, forming an abrupt termination

INFUSORIA. 57

to the simple alimentary apparatus. It should
also be mentioned that the spiral line commenced
by the circlet of cilia is continued by the vestibu-
lum and oesophagus, the longitudinal axis of which
may be considered as nearly parallel to the plane of
the ciliary disk. The position of the pharynx, on
the other hand, is perpendicular to this plane, so
as almost to correspond with the general axis of the
body.

Externally, the Vorticella is invested wdth a thin
membranous integument or * cuticle ' (l), within
which is placed the ' parenchyma of the body '
sometimes known as the ' cortical layer.' In the
substance of the latter may usually be seen the
' contractile vesicle ' (/c), which lies close beneath
the cuticle, near the anterior extremity of the
body. In contact with the parenchymatous layer
may also be detected the peculiar band-like body
termed the ' nucleus ' (z^), the position of which
would seem to vary in different individuals. The
' stalk' of the Vorticella consists of a tubular
prolongation of the cuticle, having its longitudinal
axis traversed by a peculiar contractile filament
(/z.), which is regarded by some observers as the
produced apex of a special contractile layer, distinct
from the * parenchyma of the body.'

By the rapid motion of its vibratile cilia the
Vorticella is enabled to create currents in the sur-
rounding water, by means of which any alimentary
particles that may be floating therein are brought
into the neighbourhood of the vestibulum. Some
of these are rejected, whilst others are quickly
propelled through the ciliated oesophagus into the
pharynx, where they usually remain until a suflfi-
cient number become aggregated into a single mor-

58 INFUSORIA.

sel. The latter then quits the alimentary appa-
ratus and is passed into the interior of the body,
to the posterior extremity of which it runs, and
then, turning upwards, rises on that side which is
opposite the pharynx. For some time after the
morsel has passed from the pharynx it retains
the fusiform shape which it had acquired therein,
but when, changing its course, it commences to
turn upwards, it becomes somewhat globular in
form. As soon as this is the case it ceases to have
an}^ separate motion of its own, and takes part in
a general rotatory movement which is shared by
the entire contents of the interior of the body,
the nucleus alone (according to Lachmann) being
exempted. The morsel, after making one or
more circuits within the body, at length arrives
in the neighbourhood of the anus through which
it passes into the vestibulum. The final removal
of the indigestible remains of the food is effected
by means of the strong non-vibratile cilia which
arise in front of the mouth, and it is not improba-
ble that these (which must not be confounded
with the vibratile cilia belonging to the spiral) are
also employed in guarding the commencement
of the alimentary apparatus from the ingress
of coarse or adventitious particles, which might
otherwise obstruct the entrance of the oesophagus.
Though usually fixed, the Vorticella is some-
times observed to detach itself and swim slowly
about in the surrounding water ; it has also the
power, when alarmed, of contracting its stalk into
a series of spiral folds, and of again causing it to
resume its erect position, both of these movements
being performed with great rapidity.

IXFUFOEIA. 59

3. Classification. — Of the numerous me-
thods of arranging the Infusoria which, at differ-
ent times, have been proposed, those of Ehren-
berg, Dujardin, and Claparede appear to be most
worthy of attention. All these classifications must,
however, be regarded as premature, since we know
so little of the life-history of these animals that
it is by no means improbable that many appa-
rently distinct species are nothing more than
transitional conditions of more adult forms. It is
now many years since it was satisfactorily demon-
strated by Cohn, that at least e'lgld of Ehrenberg's
genera were merely so many different stages in the
development of one of the lower Algae. Hence,
in the follo\\dng account of the Infusoria, it will be
desirable to confine ourselves to the description of
those more important characteristic featm-es which
have been made the subject of renewed and care-
ful investigation, directing attention, as we pro-
ceed, to those members of the group, in which
such characteristics may most readily be observed.

4. Siizp. — The Infusoria vary considerably in
size, the greater number being invisible without
the assistance of the microscope. Thus the ave-
rage length of the body of Vorticelkif exclusive of
the stalk, may be estimated at '003 of an inch.
Stentor {fig. 13, a), which is, perhaps, the largest
of all Infusoria, attains a length of -04 of an inch,
whilst others are so minute as to present the ap-
pearance of mere moving points under the higher
powers of the most improved instruments. But,
since the true nature of these last can be judged
of only by analogy, it seems probable that they
ought rather to be regarded as vegetable monads,

60

INFUSORIA.

or embryos, either of higher animals or true hi'
fusoria.

5. Form and §4ruetiire, — In outward form
the Infusoria may be said to vary indefinitely, all
being, however, more or less rounded (figs. 13 and
14). The presence of a simple spu'ally contrac-
tile stalk is especially characteristic of the true

Fig. 13.

Various forms of Infusoria : — a, Stentor Miilleii ; b, Chi-
lodon cucullulus; c, Oxytricha gihba ; d, Aspidisca lynceus; e,
Euplotes patella (under view) ; e', the same (side view) ; /, Pe-
ranerna globulosa ; g, Vaginicola crystallina.

Vorticellce ; in other stalked forms, the pedicle is
either rigid as in Epistylis, or branched as in
CarchesiiiTii and Zoothamoihion, Vaginicola (fig.
13, g) has the body protected by a membranous or

nsFUSOBIA.

61

horny 'carapace,' wdthin which the animal can re-
treat when alarmed ; and, in some cases, additional
protection would seem to be afforded by a valve
placed obliquely across the upper end of this
sheath (^fig, 14, a). In Lagotia (b) the rotatory
organ terminates in a pair of mde ciliated lobes
which are seldom seen at rest during: the life of
the animal. In Ophrydhnriy the most anomalous.

Fig. 14.

Marine Infusoria : — o, Vaginicola valvata, showing animal
extended and valve (^) raised ; a', the same, showing animal
contracted within its sheath and valve (<^') shut down ; — b,
Lagotia viiidis, showing rotatory organ | ; b', young animal of
preceding,

perhaps, of all the true Infusoria, the several
animalcules, though sometimes foimd detached,
are more frequently embedded in the interior of a
greenish gelatinous substance, which sometimes
occurs in masses of such extent as to have been

62 INFUSORIA.

mistaken for frog's spawn, to which, in consist-
ence, it bears some resemblance.

Anatomically, the bodies of most Infusoria may
be regarded as consisting essentially of three dis-
tinct structures, viz. : —

1. The cuticle or integument ("pellicula" of

Carter) on which are borne the cilia and
other locomotive apparatus {fig, 12, c — c) ;

2. The cortical layer or parenchyma of the body

(" diaphane " of Carter) (f ) ; and

3. The chyme mass, abdominal cavity, or in-

terior of the body (sarcode or "abdominal
mucus '' of Carter), wdthin which the particles
of the food rotate.

It is not certain whether the carapace, w^ith
which some Infusoria are provided, be distinct
from the cuticle properly so called. We have
already seen how, in Vaginicola and its allies, it
is so far separated from the rest of the body as to
act the part of a protective sheath.

Of the above structures, the second alone pos-
sesses any contractile power.

In those Infusoria which are attached, e. g.
Vorticellaf the free extremity of the body which
bears the ciliary disk is termed " anterior," the
end remote from this being said to be " poste-
rior." The term " ventral " is usually ajDplied
to that side of the body on which the mouth is
placed.

6. Digestive apparatus. — In all those In-
fusoria whose animal nature has been placed above
suspicion the presence of a mouth must be re-
garded as universal, though the position of this
organ varies considerably among the different

INFUSORIA. 63

members of tlie group. The mouth is often sur-
rounded with cilia. These cilia, as we have seen
in the case of Vorticella, are usually continued
into the oesophagus, though the latter would seem
to be in some cases destitute of these appendages.
In most Infusotia the oesophagus presents the
appearance of an open tube, freely hanging down
into the cavity of the body; but in some of these
animals it is completely collapsed, and it is only in
Vorticella and a few of its allies that it has been
observed to widen below into a pharjrnx. Eecently,
however, it has been proved by the observations of
Lieberkiihn, that in Trachelius and Loxodes the
oesophagus is continued into a peculiar ramified
canal. In other Infusoria it is altogether wanting,
and in these the alimentary apparatus consists
merely of a mouth leading into a cavity excavated
through the parenchyma of the body. In Ghilo-
don and Nassula, the interior of the oesophagus is
provided with a number of peculiar rod-like "teeth''
arranged in the form of a cylinder (fig' 13, h).
Besides the oral orifice, many Infusoria are pro-
vided with an anus, which in Steoitor, Vorticella,
and certain of their allies, is situated not far from
the mouth, close beneath the surface of the disk,
whilst in others, e. g. Biirsaria, it is placed at the
posterior extremity of the body.

7. Contractile vesicle. — We have already
noticed in A'tnoeba and ActinopJwys the existence
of certain clear spaces which occur in the substance
of the body, and in which movements of con-
traction and dilatation have been seen to take
place. Similar contractile vesicles have been ob-
served in most of the true Infusoria, being usually
situated in some part of the parenchyma of the body

64 IXFUSOPJA.

{fig* 12, k). In their dilated condition these ve-
sicles would seem to be filled with a clear fluid,
which suddenly disappears when they contract.
It may, in some cases, be noticed that the vesicles
are furnished mth branches or processes, and
Lachmann asserts that he has seen two such pro-
cesses issue from the large contractile space of
Steator polymorphiis, the one annular, running
beneath the surface of the ciliary disk, the other
longitudinal, proceeding to the posterior extremity
of the body. "WTien the vesicle contracts, both of
these " vessels " suddenly expand, the longitudinal
vessel, in particular, being seen to present nu-
merous dilatations. At the same time two rounded
expansions make their appearance in the annular
vessel, the one being situated in the neighbour-
hood of the anus, the other lying close to the
oesophagus, on the ventral surface of the body.
When the contractile vesicle reappears, both of
these vessels gradually decrease, " apparently ^Yith.-
out any contraction of their own." In healthy spe-
cimens of Bursaria, Ophryoglena, and Pavame-
chwif the contractile vesicles, together with their
associated vessels, assume a peculiar stellate form.
These and other similar appearances, observed in
the bodies of various InfusoAa, are supposed by
some to present us mth what may, perhaps, be
termed a rudimentary apparatus of circulation.

It seems proper to distinguish the above con-
tractile vesicles from certain other clear spaces
which have received from Dujardin the name of
" vacuoles." These may make their appearance
in any part of the interior of the body, and are
usually observable within a short period after food
has been swallowed. They may readily be known

INFUSORIA. 65

from true 'vesicles' by the variations wliich con-
tinually occur in their size, number, and position.

8. ;^'isc3oMs &v. — Most, ifnot all, of the77i/i(,-
soria are provided with one or more central solid
particles or ' nuclei,' the presence of which we
have already stated to be more or less charac-
teristic of the Protozoa. The nucleus varies in
position, being in most cases attached to some
part of the parenchyma of the body. It varies
also both in form and structure. Thus in Vorti-
cella and Stentor it is elongated, band-like, con-
sisting of an external membrane filled with granu-
lar contents, whilst in Ophryoglena (according to
Lieberkiihn) it is ovate, and destitute of any ap-
parent structure. In other Infusoria it may be
either round {Oxytricha), reniform {Loxodes),
shaped like a horse-shoe (Eitplotes), or spiral (as
in some species of Stentor). Sometimes, though
rarel}^, it is branched. In colour it is usually pale
yellow.

In the o-ranular contents of some nuclei a cleai*
space or cavity is observable, within which a smaller
body termed the * nucleolus ' is placed. In other
cases it occurs on the exterior of the same orc^an.
Lieberkiihn describes the nucleolus of Ophryoglena
as minute, globular, structureless, and firmly at-
tached to the surface of the ovate nucleus. But
in Chilodon, the centre of the nucleolus is marked
by a transparent dot.

A bright coloured particle (usually red), termed
the ^pigment-spot,' is found in the bodies of
many Infiisoria. In some it is altogether desti-
tute of structure, in others it is made up of a
number of exceedingly minute granules.

66 INFUSORIA.

In Opkryoglena flavicans a remarkable body
termed the " watch-glass-like organ " has been
recentW observed by Lieberkiihn. It is colourless,
transparent, homogeneous, and immovable, with
its convex side turned towards the pigment spot,
whilst its concave side is directed towards the
point of the head. It has also been detected in
Bursaria flava. Its use (as also that of the pig
ment spot) is unknown.

9. Urticating organ*^. — In the cortical layer
of Bursaria, certain peculiar fusiform bodies or
' trichocysts ' have been detected, and from these
Prof. Allman states that he has observed the emis-
sion of minute filaments which bear some resem-
blance to the urticating organs of the fresh-water
polype. They occm-, also, in other Infusoria.

10. liO€»oiiiJ>tlve orgaes. — In by far tho
greater number of Infusoria locomotion is effected
by the vibratile movements of the peculiar hair-
like appendages usually denominated cilia. The
cause of these movements is at present unknown,
nor is it certain vv^hether they are dependent
upon volition. The cilia vary in position and
mode of arrangement among the several members
of the group. Thus, in Enclielys they are scat-
tered, apparently without order, over the entire
surface of the body ; in Vorticella and Vaginicola
they are confined to the neighbourhood of the an-
terior extremity, whilst in Paramecimn and its
allies they are disposed in a series of regular rows,
parallel to one another. In other Infusoria they
either surround the entire marg-in of the flattened
body, or encircle it in the form of an oblique

iNFusorviA. 67

spiral. In Trichodina there is a crown of cilia on
the back, in addition to which a peculiar undula-
tory merabrane, richly furnished with these minute
organs, occurs on the ventral surface of the body.

In form the cilia may be described as elongated,
broader at the base than at the tip, being usually
somewhat flattened. They vaiy in length from
•02 to about '00005 of an inch. Their motion is
mostly uniform, each of the cilia bending in rapid
succession from its base to its point, and returning
immediately to its original condition : sometimes
these movements suddenly cease, but after a mo-
ment's pause they are again resumed either in
the same or in an opposite direction. From their
minute size the cilia are often difficult of detection.
Their presence, in many cases, can hardly be ascer-
tained until their motion has very much slackened,
or it may be indirectly inferred from the agita-
tion of floating particles caused by the cm-rents
w^hich are excited in the surrounding water.

By means of these cilia, the Infusoria move ra-
pidly about in the water wherein they are found,
and it is curious to observe how, when a number
are confined to a small portion of that fluid, they
rarely seem to come into collision with one an-
other or any obstacles which may be placed in their
way.

Besides the true cilia, other appendages, of ap-
parently similar natm-e, but larger size, are met
with among many Infusmia, Such, for example,
are the ^ setae' or ciliary bristles of Oxytricha
(/5''T3, c), the ^ uncini ' (hooks) and 'styles' of
Euplotes (e, e'), and the 'flagelliform filaments'
of Peranema (/). The latter may be described as
long filamentous prolongations, proceeding from

•s 2

68 INFUSORIA.

the anterior extremity of the body, their termina-
tions only being capable of performing vibratory
movements. But there is reason to infer that
many of the organisms in which they occur are, in
all probability, members of the vegetable king-
dom.

All the above appendages are properly to be
regarded as elongated processes of the cuticular
layer. It has been asserted by some observers
that each of the cilia arises from the apex of a
four-sided prism. But further observation on this
point is necessary.

The contractile movements which the stalk of
Vortioella undergoes have been described in our
account of that Infusorium.

II. BovclopiBient. — Propagation is effected
among the Infusoria by

a. Fission,
h. Gremmation,

c. Encystation, and

d. True reproduction (i. e. by ova and sper-

matozoa) ?

Of these the three first tend to separate the
individual into a number of seemingly independ-
ent beings or ' zooids,' while the fourth method
gives rise to new individuals. For an individual
(in Zoology) is equal to *'the total result of the
development of a simple ovum."

a. Multiplication by the method of fissipa-
rous division is of frequent occurrence. It may
be either longitudinal (Vorticella), or transverse
(Stentor), or either indifferently {Chilodon, Eu-
plotes, Parameciuni). It is usually stated that

INFUSORIA. 69

tlie process of separation first commences in the
nucleus, but this is incorrect, since in some cases
its division into two parts is not effected until
that of the body is nearly complete, or it may
happen that fission of the nucleus is not partici-
pated in by the body as a whole.

h. Geniination (or the development of buds)
takes place far less frequently than fission. It is
best seen in Vorticella. Here a bud is formed
(usually near the posterior extremity of the bod}^)
by the expansion of a portion of the cortical layer.
This at first derives its nutriment by means of a
diverticulum or prolongation proceeding from the
digestive cavity of the parent animal. At length
this connection is interrupted, the bud becomes
furnished with a posterior circlet of cilia, by the
aid of which it finally detaches itself and S"v\T[ms
freely about in the surrounding water {fig. 1 2, 3).
It should, however, be borne in mind that the dif-
ference between fission and gemmation is more
apparent than real, and in many cases it is im-
possible to distinguish the one from the other.

c. Some Infusoria, previously to undergoing fis-
sion, become coated with a secretion of gelatinous
matter which gradually hardens so as to enclose
the body in a ^cyst.' In other cases, peculiar
vesicular bodies become formed in the interior of
such cysts, through which they finally burst, and,
becoming ruptured at the apex, give exit to the
embryos contained in their interior. But it would
appear, from recent observations, that the pre-
vious formation of a cyst is by no means necessa-
rily antecedent to the production of the vesicles
in question.

According to Stein, the process of encystation

F 3

ro

iNFrsoraA.

is sometimes followed by a remarkable snccession
of phenomena, which have been thus described
by their discoverer, as they occur in the case of
Vorticella 'microstoma {fig. 15). An old Vor-
ticella loses or retracts its cilia, becomes encysted
{a) and finally drops off its stalk (6). The
cyst may either burst and discharge its contents

Fig. 15.

Development of Vokticei.la microstoma : — a, old Vorti-
cella in its encysted state, the nncleus and contractile vesicle
being visible within the body ; b, the same, detached from its
stalk ; c, cyst discharging its contents ; d, the band-like nucleus,
isolated ; e, Acineta form of encysted Vorticella ; f, stalked Aci-
neta (^ = Podophyra) form of the same ; g, two Acineta forms in
a state of conjugation j h, two Podophyra forms in the same con-
dition.

in the manner already indicated (c), or become
changed into an '^ Acineta form " {e). The latter
may subsequently develop a stalk, so as to as-
sume the appearance of a " Fodophyra " (/ ). In
either instance, the band-like nucleus becomes
transformed into a peculiar ovate body, the narrow
end of which is provided with a circlet of vibratile
cilia, whilst a mouth leading into an internal

iNrrsoRiA. 71

cavity soon becomes formed at its opposite extre-
mity*^; at the same time a nucleus and contractile
vesicle may be observed in its interior, Ultimately
tlie ovate body escapes through a rupture formed
in the wall of the cyst, which soon after closes,
and after a while a new nucleus is produced in
its interior, which in its turn may become trans-
formed in the same manner as its predecessor.

Relations somewhat similar to those which con-
nect Vorticella and Aclneta have been affirmed by
Haime to exist between Aspidisca (or Trichoda)
{fig, 13, d) and Oxytricha (c).

If these statements be admitted as true, it
follows that important modifications will be thereby
effected in our views as to what constitutes a
" genus " or " species " among the Infusoria; since
they would appear to show that ' Acineta^ and
Podojjliyra, usually considered to be distinct genera,
are rather to be regarded as intermediate or transi-
tional forms produced by the metaphormosis of
encysted Vorticellce. But the conclusions of Stein
have recently been altogether rejected by Lach-
niann and others, who assert that in none of his
observations did he take sufficient care to isolate
the specimens submitted to examination.

It sometimes happens that two or more Infu-
soria cohere together, but in an imperfect manner,
a line of demarcation being always observable

between them {fig. iS^ 9 ^^^ ^)' ^^ ^^^^ union
(the object of which has not yet been ascertained)
the term "conjugation" is often improperly applied.
d. Under the head of true reproduction the
following series of changes, recently observed in
Paramecium by Balbiani, would seem to be de-
serving of mention. Two Paramecicc adhere toge-

F 4

72 INFUSOEIA.

ther, their months being closely applied to one
another, and in this condition they move rapidly
through the water wherein they are confined.
Next, the nucleolus of each undergoes a consider-
able increase in size, and assumes the form of an
ovate capsule striated on its surface. It then
divides into two or four parts which increase inde-
pendently of one another, and form a number of
secondary capsules. Meanwhile the nucleus also
enlarges, becoming at the same time rounder,
wider, and softer in consistence; a number of
transjDarent spherical bodies are formed in its inte-
rior, within each of which an obscure central point
may be observed. Sometimes the nucleus breaks
up into fragments, previous to the formation of the
spherical bodies. After a certain period has been
permitted to elapse, a transfer is effected by the
two conjoined Paramecia of one or more of their
secondary capsules, which pass through the closely
appressed mouths from the body of one into that
of the other. But this does not hinder the further
increase of the capsules in size, which still con-
tinues after their transference has taken place, one
only arriving at maturity at the same time. Five
or six days after copulation minute rounded germs
make their appearance; these for a time remain
attached to the body of the parent animal by
means of the suckers "with which they are pro-
vided. At length they detach themselves, lose
their suckers, acquire a mouth in their stead, and,
becoming fm'nished with vibratile cilia, take on
the aspect of adult Parmnecia.

Such are the facts as stated by M. Balbiani.
He explains them by regarding the nucleus as an
ovar^', its contents as ovules, and each of the

INFUSORIA. 73

secondary capsules as a testis. The transference
of the capsules is then an act of fecundation, and
dissection of these bodies when fully developed
would seem to corroborate this view, since they
are found to contain numerous minute fusiform
bodies, the extremities of which are so fine as to
be almost invisible. These are said to be sper-
matozoa.

12. Histrll^iition. — The Infusoria are very
abundantly distributed over most parts of the
globe, nor does there appear to be an}^ remarkable
difference, either in aspect or organisation, between
the forms of temperate and tropical climes. They
are found plentifully in ponds, lakes, rivers, salt
marshes and the sea itself, some species, e. g.
Chilodon cuculluhts, being common to both fresh
and salt water. They occur also in many artifi-
cial infusions, and there can be little doubt that
several of these animals have been occasionally
met with as internal parasites. Those who re-
quire Infusoria for microscopic examination may,
mthout much difficulty, obtain most of the more
remarkable forms, by searching for them diligently
in suitable localities, the exact nature of which
can only be learned by experience. Thus, the
muddy sediment at the bottom of pools may be
examined for such species as avoid the light, whilst
others, on the contrary, are obtainable only by
skimminof the surface of the water. Careful in-
spection of the stems and roots of sub-aquatic
plants will often reveal the presence of Vorticella,
Vaginicolaf Stentor, and other attached forms.
The last-mentioned of these is almost \dsible to
the naked eye, and the practised observer soon

74 IJsFUSOEIA.

learns to recognise the appearance presented by
the aggregated colonies of Vorticella or Epistylis.
There are no true fossil Infusoria, the organisms
usually designated by this name being either Fo-
raminifera, Polycystina, or Diatoniacece.

13. ;Rfc^octilM«'s?. — Certain of the marine Infu-
soviet are phosphorescent, contributing, along with
other animals, to impart a luminous appearance
to the sea-water wherein they abound. But this
remarkable property is possessed in a much more
eminent degree by JS'octiluca, an organism whose

Fii). 16.

NOCTILUCA MILIARIS.

true position in the animal kingdom has long
been much misunderstood. The simplicity of its
organisation shows it to belong to the Protozoa ;
and, since it is provided with a distinct mouth, it
ought probably to be regarded as an aberrant
member of the gi'oup Infusoria. Its structure has
been of late years investigated by Quatrefages, and
Krohn, and still more recently by Mr. Huxley.
In form it is nearly globular, presenting on one
side a * hilus,' or groove, from the anterior extra-

INFUSORIA. 74

mity of which issues a peculiar curved stalk or ap-
pendage, marked by transverse lines, which would
seem to be made use of as an organ of locomotion.
Kear the base of this * tentacle ' is placed the
mouth, provided on one side with a tooth-like pro-
jection. The mouth leads into an 'oesophagus,'
from the bottom of which a delicate flickering
filament or ' cilium ' is sometimes protruded.
The oesophagus passes into a dilatable digestive
cavity which is supposed by Mr. Huxley to be con-
nected with a small funnel-shaped depression or
* anal aperture ' situated in the midst of a flattened
space behind the mouth. An oval 'nucleus,'
rather less than '002 of an inch in length, lies in
front of the digestive cavity. The body of Kocti-
luca is invested by a rather firm membrane,
destitute of cilia, beneath which occurs a gelatinous
layer richly furnished with minute granules. From
this layer arises a network of delicate granular
' fibrils,' which unite to form coarser fibres as they
proceed towards the centre of the body, until finally
they reach the nucleus and digestive cavity. The
diameter of Noctiluca varies from '04 to '01 of
an inch. It is, perhaps, the most frequent som-ce
of the diffused luminosity of the sea in tempe-
rate climes, the light which it emits being, as it
were, the combined result of a rapid succession of
vivid scintillations.

Noctiluca multiplies by spontaneous fission.
Within the body of this animal Busch observed the
existence of certain brown masses, containino- ora-
nules m their interior. It is not certain whether
these were true ova or merely the result of a
process of gemmation. In other Noctilucce the
same observer detected peculiar germ-like bodies,

76 INFUSORIA.

each furnished \vith an obtuse process. These
germs were also met with in a free condition, and
their development was traced up to a certain point,
after which Busch was obliged to discontinue his
investigations.

In the same situations as Noctiluca, Busch further
discovered numerous transparent gelatinous bodies,
of similar size and appearance, and possessino^, in
many cases, phosphorescent properties, though not
pro\ided with radiating fibres, or locomotive ap-
pendage. These bodies were almost destitute of
structure, but on a portion of their surface there
usually occurred several remarkable yellowish pro-
cesses, either rounded or tapering to a point, con-
taining in their interior minute spherical granules.
The nature of these problematical organisms pre-
sents a subject for future inquiry.

77

NOTE ON 'ACINETA FORMS/

It seems proper to conclude, with Lachmann, that
these organisms are not, as was formerly supposed,
Rhizopods allied to Actinophrys, nor yet again meta-
morphosed conditions of Vorticellcs, but that they
rather constitute a distinct group of Infusoria, to
which the term 'polystome' might, without objection,
be perhaps applied. For each of the radiating fila-
ments {fig. 15, e) with which the AciiiefcB are pro-
vided is, in truth, a retractile tube, susceptible of
elongation to a remarkable extent, and furnished at
its extremity with an adherent disk. With the aid
of these unique organs an Acineta is enabled, not
only to seize and retain its more active prey, but also
to imbibe the nutrient particles contained in the body
of the latter, by a peculiar method of suction. ^Tien
the size of the prey is considerable, this process has
been observed to occupy several hours. With the
exception of the above-mentioned mouths, no other
aperture has been hitherto discovered in the bodies
of these animals.

79

BIBLIOGRAPHY OF THE PROTOZOA.

RHIZOPODA.

a. Amceba, A>fD ITS Allies.

AuERBACH. — ' Ueber die Einzelligkeit der Amoeben.' Zeitschrift fijr
VVissenschaftliche Zoologie, 1855.

KoLLiKEPw. — ' Das Sonnenthierchen, Actinophrys sol.' Zeitschr. f.
Wiss. Zool., 1849, and Quarterly Journal of Microscopical
Science, 1853.

Bailey. — ' Observations on a newly discovered Animalcule.' Ameri-
can Journal of Science and Arts, 1853.
Also: Claparede, Miiller's Archiv, 1854, and Annals of Natural
History, 1855; Westox, Quart. Journ. Micr. Sci., 1856; and
several treatises on the Infusoria, more especially those of
DujAKDLN, Lachmann, and Claparede.

}}. FORAJVIINIFERA ; GENERAL CHARACTERS.

ScHULTZE. — 'Ueber den Organismus der Polythalamien (Fora-
miniferen) nebst Bemerkungen iiber die llhizopoden im
AUgemeinen,' 1854.

Williamson. — ' On the Recent Foraminifera of Great Britain,'
1858.
Appended to this work, which contains figures and descriptions
of the more important varieties of all the British species of
Foraminifera, will be found a very complete bibliography of
the entire group.

C. FOP.AMLNIFERA ; STRUCTURE OF THE ShELL.

Carpenter. — 'Researches on the Foraminifera.' Philosophical
Transactions, 1856-7.

80 BIBLIOGEAPHY.

Carter. — ' On the Form and Structure of Operculina Arabica.'

Ann. Nat. Hist., 1852.
Willia:>ison. — Various papers published in Quart. Journ, Micr. Sci.

d. FORAMINIFERA ; FoSSIL FoRMS.

Ehrenberg. — 'Ueber den Griinsand und seine Erlanterung des

Organischen Lebens.' Abhandlungen der Konigl. Akademie

der Wissenschaften zu Berlin, 1855.
Egger. — * Die Foraminiferen der Miocan-Schichtenbei Ortenburg in

Nieder-Bayern,' 1858.
Pictet. — 'Traite de Pale'ontologie,' 1857; and the 'Cours Ele'men-

taires de Pale'ontologie,' and ' Prodrome de Paleontologie,' of

D'Orbigny.
Other memoirs are indicated in the bibliography appended to

the monograph of Williamson, above referred to.

POLTCYSTIXA and TH.aASSICOLLID/E.

MuLi.ER, J. — ' Ueber die Thalassicollen, Polycystinen und Acantho-

metren des Mittelmeeres.' Ab. d. K. Akad. Berlin., 1858, and

Quart. Journ. Micr. Sci., 1856.
HrxLEY.— ' On Thalassicolla.' Ann. Nat. Hist., 1851.
For information on the fossil Polycystin^e see Ehrenberg,

* Mikrogeologie,' 1854; Ab. d. K. Akad. Berlin, 1846-7, and

Ann. Nat. Hist., 1847.

SPONGTD^.

BowERBANK. — ' On the Anatomy and Physiology of the Spongiadae :'
Phil. Trans., 1859. ' On the Vital Powers of the Spongiadae :'
Reports of the British Association, 1856-7; and other papers
in Ann. Nat. Hist., 1 841-2-5; and Quart. Journ. Micr. Sci.,
1859.

Hl'xley. — 'On the Anatomy of the genus Tethya.' Ann. Nat.
Hist., 1851.

Johnston. — • History of British Sponges and Lithophytes,' 1842.
Also: Carter, Ann. Nat. Hist., 1848-9-54-7; Lieberkuhn,
Mailer's Archiv, 1856-7, and Ann. Nat. Hist., 1856; Dobie,
Goodsir's Annals of Anatomy and Physiology, 1852; Han-
cock, Ann. Nat. Hist., 1849; Morris, do. do.; Owen,
Transactions of Zoological Society of London, 1841 ; Gray,
Ann. Nat. Hist., 1858. An account of the older memoirs oni

OF THE PROTOZOA. 81

Sponges -will be found in Dr. Johnston's Tvork, cited above.
With reference to the fossil Spongidae, the following papers
may be consulted : — Boaverbajstk, ' On the Siliceous Bodies
of the Chalk, Greensand and Oolite,' Transactions of Geolo-
logical Society of London, 1841 ; J. T. Smith, * On the Ven-
triculidae of the Chalk,' Ann. Nat. Hist., 1847-8. See also
PiCTET, *Trait-e de Paleontologie,' 1857; and the paleonto-
logical treatises of D'Orbigny, already alluded to.

GREGARINIDiE (including PSOROSPERMIiE).

KoLUKER. — * Beitrage zur Kenntniss niederer Thiere.' Zeitschr. f.

wiss. Zool., 1848.
LiEBERKiJHN. — ' Uebcr die Psorospermien.' Muller's Archiv, 1854.
Also Bruch, Zeitschr. f. wiss. Zool., 1850; Dufour, Annales

des Sciences Naturelles, 1828; Frantzius, ' Obsei^vationes

quaedam de Gregarinis,' 1846; Henle, Muller's Archiv, 1845;

Leidy, Transactions of American Philosophical Society, 1S51 ;

Leydig, Muller's Archiv, 1851 ; MIjller, ibid., 1841 ; Roein'

'Histoire Naturelle des Vegetaux Parasites,' 1853; Stein,

Muller's Archiv, 1848.

INFUSORIA.

Ehrexberg. — ' Die Infusionsthiere als volkommene Organismen,*
1838.

DujARDiN. — ' Infusoires,' 1841.

Stein. — ' Infusionsthiere auf ihre Entwickelungeschichte unter-
sucht,' 1854.

Lachmann et Claparede. — ' Etudes sur les Infusoires et les Rhi-
zopodes,' Memoires de I'lnstitut National Genevois, 1858;
also, Muller's Archiv, 1856, and Ann. Nat. Hist. 1857.

CoHN. — Various papers published in Zeitschr. f. wiss. Zool., 1851-
3-4 and 7.
See also the memoirs of Auerbach, Czermak, Ecker, and
CiENKOWSKY, in the same journal, together with those
of various writers in Ann. Nat. Hist., Ann. Sci. Nat.,
Muller's Archiv, and Wiegmann's Archiv. Among these
may be mentioned : Carter, Ann. Nat. Hist., 1856-9; Haime,
Ann. Sci. Nat., 1853; LieberkIjhn, Muller's Archiv, 1856-7,
and Ann. Nat. Hist., 1856 ; Schneider, Miiller's Archiv, 1854,

G

82 BIBLIOGTlArHr.

and Ann. Nat. Hist., 1854. An abstract of the contents of
Ehrenberg's work will be found in Pritchard's 'History of
Infusorial Animalcules,' and the ' Micrographic Dictionary' of
Griffith and Henfrey. Other sources of information are:
Allmann, Quart. Joum. Micr. Sci., 1855 ; Balbiani, Comptes
Rendus, 1858, and Ann. Nat. Hist., 1858 ; Focke, ' Amtlicher
Bericht der Naturforscherversammlung zu Bremen,' 1844;
Frantzius, ' Analecta ad Ophrydii versatilis historiam natu-
ralem,' 1849; Kutorga, 'Naturgeschichtederlnfusionsthiere,
verzuglich nach Ehrenberg's Beobachtungen,' 1841 ; Peltier,
L'Institut, 1836; PoucHET, Comptes Rendus, 1849, and Ann.
Nat. Hist., 1849 ; Schmidt, Froriep's Notizen, 1849 ; Huxley,
Quart. Joum. Micr. Sci., 1857; Samuelson, do. do.; and
the classical treatises of Leuwenhoek, Phil. Trans., 1676 ; C.
F. MiJLLER, ' Animalcula Infusona,' 1786; and Wrisberg,
' Observationum de Animalculis infnsoriis satura,' &c., 1765.
Also, T. S. Wright, Edinburgh New Philosophical Journal,
1858.

NOCTILUCA.

BuscH. — *Das Meerleuchten unddie Noctiluca,' in Beobachtungen,
iiber Anatomic und Entwickelung einiger wirbellosen See-
thiere, 1851.

Huxley. — * On the structure of Noctiluca miliaris.' Quart. Joum.
Micr. Sci., 1855.

Quatrefages. — * Observations sur les Noctiluques,' Ann. Sci.
Nat, 1850, and Ann. Nat. Hist, 1853.
Also: Brightwel, Ann. Nat Hist, 1850; GossE, Devonshire
Coast, p. 253, 1853; Krohn, Wiegmann's Archiv, 1852;
Lesson, Acalephes, p. 145, 1843; Pring, Philosophical Ma-
gazine, 1849; and Webb, Quart Joum. Micr. Sci., 1855.

83

QUESTIONS ON THE PROTOZOA.

1. Why is it desirable to separate Amoeba and its allies from the

true Infusoria ?

2. Compare Pamphagus with Amoeba and Difflugia.

3. What are Psorospermise ?

4. Describe the process of gemmation in Vorticella.

5. In addition to the true cilia, what other locomotive organs aro

found among the Infusoria ?

6. What animal forms were included by J. Miiller in the group Rhi-

zopoda Radiolaria ?

7. Mention some of the characters by which Grantia is distin-

guished from other Sponges.

8. How are the Polythalamia subdivided by Schultze ?

9. Into what two sections may the Rhizopoda be divided ? Distin-

guish between them.

10. Give examples of Foraminifera which occur in the primary rocks.

11. What organised beings were included among the Infusoria of

Ehrenberg ?

12. By what single anatomical feature may the Infusoria be distin-

guished from other Protozoa ?

1 3. Distinguish Polycystina from Foraminifera.

14. Give some account of the 'aquiferous system' of the Spongidae.

15. Describe the structure of the seed-like body of Spongilla.

16. Of what essential structures does the body of an Infusorium con-

sist?

17. What is meant by the term * Sarcode ' ?

18. State briefly what is known concerning the development of the

Rhizopoda.

19. What principle guided D'Orbigny in framing his classification of

the Foraminifera ?

20. To which of his groups ought Miliolina to be referred ?
2.1. Why is his arrangement objectionable?

G 2

84 QUESTIONS ON THE PEOTOZOxV.

22. How do Acanthometrae differ from Thalassicollidae ?

23. Give some account of the mode of propagation among the Gre-

garinidce.

24. Distinguish Vorticella from other stalked forms of Infusoria.

25. What is meant by the terms, 'peristome,' 'vestibulum," pharynx,'

and 'oesophagus,' as applied to the Infusoria ?

26. In the simple form of Orbitolites, how are the segments of sar-

code contained in the outermost zone connected with those of
the cells belonging to the zone immediately within it ?

27. Give examples of Foraminifera in which the 'shell' is not cal-

careous.

28. Why are Sponges regarded as members of the Animal Kingdom ?

29. Describe Gregarina Sieboldii.

30. Mention some examples of Infusoria in which the digestive

cavity is furnished with a second aperture.

31. Distinguish 'vacuoles' from 'contractile vesicles.'

2e. What is the nature of the so called ' fossil Infusoria ' ?

33. What are ThalassicoUida? ?

34. Of what geological period are Nummulites chiefly characteristic ?

35. In what group of the Astomatous Protozoa has true reproduc-

tion been proved to occur?

36. Give examples of widely distributed Foraminifera.

37. Define the terms, 'septum,' 'septal plane, and 'peripheral

margin.'

38. How is the digestive px-ocess effected in Actinophrys .?

39. How in Vorticella ?

40. Why ought all classifications of the Infusoria which have hitherto

been proposed to be considered premature ?

41. Describe the swarm spores of Spongilla.

42. Explain the mode of growth of the shell in Miliolina.

43. How is the growth of the shell supposed to take place in Orbito-

lites?
4^ What position does the ' nucleus ' occupy in the body of an
Infusorium ?

45. What is the position of the nucleolus ?

46. What functions has Balbiani ascribed to these two organs ?

47. What facts have induced him to infer that true reproduction

occurs in Paramecium ?

48. Describe NoctiluCv^ miliaris.

49. Give a resume of Stein's account of the metamorphoses of Vor-

ticella miscrostoma.

50. What is the position of the urticating organs in Bursaria ?

85

LIST OF ILLUSTRATIONS.

Page

1. Amoeba radiosa, after Auerbach 4

2. Various forms of Rhizopoda, after Ehrenberg and KoUiker 6

3. Various forms of Foraminifera, after D'Orbigny, Parker,

and Williamson 13

4. Structure of Orbitolites complanatus, after Carpenter . 19

5. Polycystina, after Ehrenberg 28

6. Structure of Grara^ia,&c., after Dobie and Williamson . 31

7. Structure of Tethya, after Huxley 38

8. Structure of seed-like body of Spongilla, after Carter . 39

9. Structure of Thalassicollidce, after Huxley 45

10. Acanthometra lanceolata, after J ]\I tiller . . . .47

11. Cr re^anw« and Psorosper?ni<E, after Kolliker and Kobin . 50

12. Structure of Vorticella, &c., after Ehrenberg and Lachmann 55

13. Various forms of Infusoria, after Dujardin and Ehrenberg . 60
14 Marine hifusoria, after Strethill Wright . . . .61

15. Development of Vorticella microstoma, after Stein . . 70

16. Noctiluca miliaris, after Quatrefages , .... 74

86

INDEX.

Acanthometrtc, 47, 48.

Acervulina, if.

Acineta forms, 70, 71, 77.

Aclinophrys, 6, 7, 8, 26.

Actinospongia, 42.

Agathistega, 10, 11.

Amoeba, 3-6, 8.

Atnoebea, 8.

Amcebina, 8.

Anal aperture, of Infusoria^ 56, 6j ; of

Noctiluca, 75.
Animal nature, of Sponpes, 30.
Aquiferous system, of Sponges, 32.
Arcella, 8.
Arcellina, 8.
Aspidisca, 71.
Astomata, 2.

Bristle, of Vorlicella, 56.
Bursaria, 63, 64, 66.

Canals, of Polythalamia, 17 ; of
Sponges, 33.

Carapace, of Hhizopoda, 8 ; of Infuso-
ria, 61, 62.

Carchesiuni, 60.

Carpenter ia, 43.

Cassidulina, 15.

Chilodon, 63, 65, 68, 73.

Cilia, of Sponges, 30, 345 of Infusoria,
56, 66-68.

Circulatory movements, in Sponges,
33, 34 ; in Infusoria, 64.

Classification, of Protozoa, 2 ; of
Rhixopoda, 8 ; of Foraminifera, 9 ;
of SpongidcE, 36 ; of Tkalassicollidce,
Polycystina, and Acanthoiyictra;, 48 ;
of Gregarinid(Z, 51 ; of Infusoria, 59.

Cliona, 42.

Cceloptychium, 42.

CoUosphcera, 46.

Collosp/icsridiE, 48.

Contractile vesicle, of Protozoa, i ;
of Amoeba, 5 ; of Infusoria, 57, 63.

Cortical layer, of Infusoria, 57, 62.

Cristellaria, 15.

Cuticle, of Infusoria, 57, 62.

Cycloclypeus, 26.

Dentalina, 14.

Dermal membrane, of Sponges, 34.

Development, of Rkizopoda, 26 ; of

SpongidtE, 39 ; of Gregarinidw, 50 ; of

Infusoria, 08 ; of Noctiluca, 75.
Diaphane, 6a.
Didimophydie, 51.
Difflugia', 8, 26.
Digestive apparatus, of Infusoria, 62 ;

of Noctiluca, 75.
Disk, of Vorticella, 56.
Distribution, of Foraminifera, 23 — 26;

of Polycystina, 29; of Infusoria, 73.
Dujardinia, 43.

Enallostega. 10, 11.

Enchelys, 66.

Encystation, of Infusoria, 68, 69.

Ento?nostega. 10, 11.

Entosolcnia, 14.

Fpistylis, 60.

Euplotes, 65, 67, 68.

Faujasina, 17.

Fibre, of Sponges, 32.

Fission, of Rhixopoda, 26 ; of Infusoria,

68.
Flagelliform filaments, of Infusoria, S-^.
Foraminifera, 8, 9 ; classification of, 9 ;

unilocular forms of, 13 ; multilocular

forms of, 14; structure of the shell

in, 15—21; distribution of, 23—26;

fossil forms of, 24, 25 ; size of, 26 ;

affinity of. to Sponges, 43.
Fossil remains, of Foraminifera, 24, 25 ;

of Polycystina, 29 ; of Spongidce, 42 ;

of Infusoria, 74.
Frondicularia, 14.
Fusulina, 24.

Gemmation, of Foraminifera, 15; of

Infusoria, 69.
Globigerina, 23.
Goniospongia, 42.
Grantia, 30, 32, 36.
Gregarinarice, 51.
Gregarinidee, 2, 49 ; development of,

50 ; classification of, 51.

INDEX.

87

Gromia, ij,2i.
Gutlulina, 24.
Helicoidea, 10, 11.
Hrlicostega, 10, 11, 15.
Hetnispongia, 42.

Infusoria, 2, 5J ; structure of, 55—58,
60—66 ; classification of, 59 ; size of,
59 ^ urticating organs of, 66; loco-
motive organs of, 66 ; development
of, 68 ; distribution of, 7}.

Lagena, ij, 21.

Lagotia, 61.

Litigulina, 14, 2j.

Locomotive organs, of Infusoria, 66.

Loxodes, 6j, 65.

Meandrospongia, 42.
Miliolina, 15, 21.
Miliolince, 10.
Monocystideee, 51.
Monostega, 10. 11.
Multilocular Foraminifera, 14.

Nnssula, 6j.

Nautiloid Foraminifera, 14, 22.

Noctiluoa, 74.

Nddosaria, 14.

Nonionina, 26.

Nucleolus, of Infusoria, 65.

Nucleus, of Protozoa, i ; of Amoeba,
5 ; of Spharozoum, 44 ; of Gregori-
nidce, 49; of Infusurta, 65; of Aoc-
tiluca, 75.

Nummulites, 15, 16, 17, 25, 26.

Nummulitic formation, extent of, 25.

CEsophagus, of Infusoria, 56, 6j ; of

Noctiluca, 75.
Operculina, 17.
Ophrydium, 61.
Ophryoglenn, 64, 65, 66.
Orhituides, 26.
Orbitolites, 17—21, 26.
Orbulina, 2j.
Oscula, of Sponges, 33.
Ova, of Tethya, j8.
Oxytricha, 65, 67, 71.

Palcvospongia, 42.
Pamphagus, 8.
Paramecium, 64, 66, 68, 71.
Parenchyma of the bodj-, of Infusoria,

57, 62.
Pellicula, 62.
Peranema, 67.
Perispongia, 42.
Peristome, of Voriicella, 56.
Pharynx, of VorticellcB., 56, 63.
Phosphorescence, of Infusoria, 74 ; of

Noctiluca, 74, 75.
Pigment spot, oi Infusoria. 65.
Pleurostoma, 42.
Podophyra forms, 70, 71.

Polycystina, z, 28, 48 ; distribution of,

29.
Polygastrtca, of Ehrenberg, 53.
Puiystonielui, 15, 16.
Polythalamia, 10, il, T4.
Pores, of Sponges, 33.
Proteonina, 21,
Protozoa, general characters of. 1 ;

classification of, 2.
Pseudo-naviculae, of Gregarinida; 50,

51-

Pseudopodia, of Rhizopoda, J, 6, 9; of

Polycystina, 29.
Psorospermice, 51.

Radiolaria, 48.

Reparative powers, of Sponges, 35.

Reproduction, of Spongidce, 39 j of
Infusoria, 71.

Retispongia, 42.

Rhabdoidea, 10, 11.

Rhizopoda, 2, 3 ; nature of, 6 : classifi-
cation of, 8; size of, 26; develop-
ment of, 26.

Rhizopoda radiolaria, 47, 48.

Rotalia, 24, 25.

Rotatory organ, of Voriicella, 56.

Sarcode, 6, 9, 29, 62.

Seed-like body, of Spongilla, 40.

Setas, of Infusoria, 67.

Shelly covering, of Foraminifera, 9,

13-23 ; of Polycystina, 28 ; of Cf/-

li.'fjiheBra , 46.
Size, of Rhizopoda, 26 ; of Spongidw,

3 1 ; of Thalassicollidce, 44 ; of /«/m-

soria, 59 ; of Noctiluca, 75.
Skeleton, of Sponges, 32.
Soroidea, 10, 11.
Spermatozoa, of Tethya, 38.
Sphcerozoum, 44.
SphwrozomidcB, 48.
Spicula, of Spongidee, 35, 37, 40 ; of

TlialassicoUidce, 45.
Spirulina, 25.
Spongidcs, 2, 30 ; animal nature of, 30 ;

form and size of, 31 ; skeleton of, 32;

aquiferous system of, 32; reparatiie

powers of, 35 ; spicula ot, 35 ; classifi-

cati')n of, 36; development of, 39;

distribution of, 42; fossil forms of,

42; affinity of, to Foraminifera, 43.
Spongilla, 30, 34, 36, 39; .«eed-like

bodies of, 40; swarm spores of, 41.
Stalk, of Vurticetia, 57, 58.
Starch granules, in Aynoeba, 6.
Stentor, 59, 63, 65, 68, 73.
Stichoste^a. 10, il.
Styles, ol Infusoria, 67.
Swarm spores, of Spongilla, 41.

Technical terms, applied to shells of

Rhizopoda, z\.
Teeth, of Chilodon and Nassula, 63.
Tentacle, of Noctiluca, 75
Tethya, structure of, 37.

88

INDEX.

Textularla, 15, 16, 24, Z5.

Thalamospon^id, 4Z.
Thalassiculla, 45.
'I halassicollidce, z, 44.
Thalassicollina, 48.
1'ooth, of Noctiluca, 75.
Trachelius. 6j.
Trichocysts, of Bursaria, 66.
Trichoda, 71.
Trichodina, 67.

Troclioid Foraviinifera, 16, 24.
Turonia, 42.

Uncini, of Infusoria. 67.
Unilocular Foraminijera. ij.
Urticating organs, of Injusuria, 66.
Vacuoles, 7, 64.
Vaginicola, 60, 66.
Vestibulum, of Vorticella, 56.
VorticcUa, 55—58, 59, 60, 6z, 63, 65, 66 ;
development of, 68—71 .

Watchglass-like orean, of Injusoria,

66.
Ztioi/iamniuin, 60.

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