CHAPTER IV.

ZOOPHYTES.

"Nature is nowhere more perfect than in her smaller works."

"Natura nusquam magis quàm in minimis tota est."

PLINY.

It will not be out of place here to offer some remarks on animals in

general, including the whole kingdom as well as the great divisions

which form the subject of this particular volume. But considering the

vastness of the subject, and our imperfect knowledge of the whole animal

series as a subject of study, nothing is more difficult than to seize

upon the real analogies between beings of types so varied,--of

organizations so dissimilar. The arrangements which naturalists have

established in order to study and describe animals--the divisions,

classes, orders, families, genera, and species--are admirable

contrivances for facilitating the study of creatures numerous as the

sands of the sea shore. Without this precious means of logical

distribution, the individual mind would recoil before the task of

describing the innumerable phalanges of contemporary animal life. But

the reader must never forget that these methodical divisions are pure

fictions, due to human invention: they form no part of nature; for has

not Linnæus told us that nature makes no leaps, _natura non facit

saltus_? Nature passes in a manner almost insensibly from one stage of

organization to another, altogether irrespective of human systems.

Moreover, when we come to watch the confines of the animal and vegetable

kingdom, we realise how difficult it is to seize the precise line of

demarcation which separates the great kingdoms of Nature. We have seen

in the "Vegetable World" germs of the simplest organization, as in the

Cryptogamia, spores, as in the Algæ, and fruitful corpuscles, as in the

Mosses, which seem to be invested with some of the characteristics of

animal life, for they appear to be gifted with organs of locomotion,

namely, vibratile cilia, by means of which they execute movements which

are to all appearance quite voluntary. Side by side with these are

vegetable germs and fecundating corpuscles, known as _antherozoides_

among the Algæ, Mosses, and Ferns, which, when floating in water, go and

come like the inferior animals, seeking to penetrate into cavities,

withdrawing themselves, returning again, and again introducing

themselves, and exhibiting all the signs of an apparent effort. Let us

compare the Infusoria, or even the Polypi and Gorgons, with these

shifting vegetable organisms, and say if it is easy to determine,

without considerable study, which is the plant and which the animal. The

precise line of demarcation which it is so desirable to establish

between the two kingdoms of Nature is indeed difficult to trace.

The word _zoophyte_, to which this comparison introduces us, seems very

happily applied: it is derived from the Greek word ζῶον, animal, and

φυτὸν, _plant_; and is, as it seems to us, quite worthy of being

retained in Science, because it consecrates and materialises, so to

speak, a sort of fusion between the two kingdoms of Nature at their

confines. Let us guard ourselves, however, from carrying this idea too

far, and, upon the faith of a happy word, altering altogether the true

relations of created beings. In adopting the name _zoophyte_, to

indicate a great division of the animal kingdom, the reader must not

imagine that there is any ambiguity about the creatures designated, or

that they belong at once to both kingdoms, or that they might be ranged

indifferently in the one or the other. Zoophytes are animals, and

nothing but animals; the justification for using a designation which

signifies animal-plant is, that many of them have an exterior

resemblance to plants; that they divide themselves by offshoots, as some

plants do, and are sometimes crowned with organs tinted with lively

colours, like some flowers.

This analogy between plants and zoophytes is nowhere more apparent than

in the coral. Rooted in the soil and upon rocks, the form of its

branches many times subdivided, above all, the coloured appendages which

at certain periods so closely resemble the corolla of a flower, have all

the form and appearance of plants. Until the eighteenth century most

naturalists classed the coral as Linnæus did, without the least

hesitation, with analogous creations in the vegetable world. Réaumur

long contended for the contrary opinion; but it is only in our day that

the animal nature of the coral is satisfactorily established. The _sea

anemone_ may be cited as another striking example of the resemblance

borne by certain inferior organisms to vegetables. We hold, then, that

we are justified in using the word _zoophyte_ to designate the beings

which now occupy our attention.

* * * * *

We shall not surprise our readers by telling them that the structure of

the zoophyte, especially in its inferior orders, is excessively simple.

They are the first steps in the scale of animal life, and in them a

purely rudimentary organization was to be expected. In these

beings--true types of animal life--the several parts of the body, in

place of being disposed in pairs on each side of its longitudinal plane,

as occurs in animals of a higher organization, are found to radiate

habitually round an axis or central point, and this whether in its adult

or juvenile state. Zoophytes have not generally an articulate skeleton,

either exterior or interior, and their nervous system, where it exists,

is very slightly developed. The organs of the senses, other than those

of touch, are altogether absent in the greater part of beings which

belong to this, the lowest class of the last division of the animal

kingdom.

Several questions arise here: Has the zoophyte sentiment, feeling,

perception? Has it consciousness, sense, sensibility? The question is

insoluble; it is an abyss of obscurity. The coral, or rather the

aggregation of living beings which bear the name, are attached to the

rock which has seen their birth, and which will witness their death: the

infusoria, of microscopic dimensions, which revolve perpetually in a

circle infinitesimally small; the Amoebæ, the marvellous Proteus, which

in the space of a minute changes its form a hundred times under the

surprised eyes of the observer, are, in truth, mere atoms charged with

life. Yet all these beings have an existence to appearance purely

vegetative. In their obscure and blind impulse, have they consciousness

or instinct? Do they know what takes place at the three-thousandth part

of an inch from their microscopic bodies? To the Creator alone does the

knowledge of this mystery belong.

It would be foreign to the object of this work to enter into minute

division of the innumerable creatures which swarm on the ocean and on

its confines. We shall perhaps best consult the convenience of our

readers by adopting the following simple arrangement of these animals

into

I. PROTOZOA, including the _Spongiadæ_, _Infusoria_, and _Foraminifera_.

II. POLYPIFERA, including the _Hydræ_, _Sertularia_, and _Pennatulariæ_.

III. ECHINODERMATA, or Sea-urchins and Star-fishes.

Our space will prevent our doing more than presenting to the reader in

succession the most characteristic types of each of these groups.

I. THE PROTOZOA.

The Protozoares represent animal life reduced to its most simple

expression. They are organized atoms, mere animated and moving points,

living sparks. As they are the simplest forms of animal life as regards

their structure, so also they are the smallest. Their microscopic

dimensions hide them from our view. The discovery of the microscope was

a necessary step to our becoming acquainted with these beings, whose

existence was ignored by the ancient world, and only revealed in the

seventeenth century by the discovery of the microscope. When armed with

this marvellous instrument, applied to examine the various liquid

mediums--as when Leuwenhoek, for example, applied the magnifying glass

to the inspection of stagnant water, with its infusions of macerated

vegetable and animal substances--when he scrutinized a drop of water

borrowed from the ocean, from rivers, or from lakes, he discovered there

a new world--a world which will be unveiled in these pages.

Some modern writers believe that the Protozoa is a mere _cellular

organism_, that being the principle and end of organization, such as we

find it in the cellular vegetable. According to this hypothesis, the

Protozoares would be the cellulars of the animal kingdom, as the Algæ

and Mushrooms are of the vegetable world. This idea is so far wrong,

that it has been founded upon the empire of pure theory. "In reality,"

says Paul Gervais and Van Beneden, "the animals to which we extend it

very rarely resemble elementary cellulars." The tissue of which the

bodies of the Protozoa are composed is habitually destitute of cellular

structure. They are formed of a sort of animated jelly, amorphous and

diaphanous, and have received from Dujardin the name of _Sarcoda_, or

soft-fleshed animals.

Infinitely varied in their form, the Protozoares are furnished with

_vibratile cilia_, which are organs of locomotion belonging to the lower

animals inhabiting the liquid element. Their bodies are sometimes naked,

sometimes covered with a siliceous, chalky, or membranous cuirass. They

are divided into two great classes, the _Rhizopoda_ and _Infusoria_.

SPONGIA.

The Sponge is a natural production, which has been known from times of

the highest antiquity. Aristotle, Pliny, and all other writers who

occupied themselves with natural history in ancient times, are agreed in

according to it a sensitive life. They recognize the curious fact that

the sponge evades the hand which tries to seize it, and clings to the

rocks on which it is rooted, as if it would resist the efforts made to

detach it. Pliny, Dioscorides, and their commentators, even formed the

idea that sponges were capable of feeling, that they adhered to their

native rock by special force, and that they shrunk from the hand which

tried to seize them. They even distinguished males from females.

Erasmus, however, criticising Pliny, concludes that he may pass over all

he has written upon the sponge. The sponge, in short, was to the

ancients something between a plant and an animal.

Rondelet, the friend of the celebrated Rabelais, whom the merry curate

of Meudon designated under the name of _Rondibilis_, who was himself a

physician and naturalist of Montpellier, denied at first the existence

of sensibility in sponges. He originated the idea that these productions

belonged to the vegetable world--an idea which Tournefort, Gaspard

Bauhin, Rey, and even Linnæus, in the first editions of his "Systema

Naturæ," supported by the great authority of their names. Afterwards,

influenced by the convincing labours of Trembley and some other

observers, Linnæus withdrew the sponges from the vegetable world. He

satisfied himself, in short, that certain polypiers much resembled

sponges in the nature of their parenchyma, and that, on the other hand,

the assimilation of sponges with plants was not such as could be

maintained. Neuremberg, Peyssonnel, and Trembley maintain the animal

nature of sponges, and their views are adopted by Linnæus, Guettard,

Donati, Lamouroux, and Ehrenberg on the Continent, and by Ellis,

Fleming, and Grant in England. They live at the bottom of the seas in

five to twenty-five fathoms of water, among the clefts and crevices of

the rocks, always adhering and attaching themselves, not only to

inorganic bodies, but even growing on vegetables and animals, spreading,

erect, or pendent, according to the body which supports them and their

natural habit.

The power of fixing themselves to other objects, which certain animals

possess, is very singular. Nevertheless, it is certain that whole tribes

exist consisting of innumerable strictly adherent species, which live

and die attached to some rock or other object; and among these are all

polypiers, such as the sponges and corallines. It follows that they are

wholly dependent on external agencies for their means of existence. "The

poor little creatures," says Alfred Frédol, "receive their nourishment

from the wave which washes past them; they inhale and respire the bitter

water all their lives; they are insensible to that which is only the

hundredth part of an inch from their mouth."

In the months of April and May, these animalcules engender germs, round,

yellow, or white, whence proceed certain ovoid granular embryos

furnished towards their largest extremity with small vibratile cilia.

They are thrown off by the currents, which serve as a stomach, and form

swarms of larvæ round the polypier. They swim about with a gliding wavy

motion, and when they have been some time in the water they usually come

to the surface; but they are also often carried off by the current.

During two or three days they seem to seek a convenient place to fix

themselves. Once fixed, the larvæ loses the cilia, spreads itself out,

and takes the form of a flattened gelatinous disk.

Its interior organization consists of contractile cellules and numerous

spiculæ--"a tribe," says Gosse, "of the most debateable forms of life,

long denied a right to stand in the animal ranks at all, and even still

admitted there doubtingly and grudgingly by some excellent naturalists.

Yet such they certainly are, established beyond reasonable controversy

as true and proper examples of animal life."

It may, then, be safely asserted that all naturalists are now satisfied

of the animal nature of sponges, although they represent the lowest and

most obscure grade of animal existence, and that so close to the

confines of the vegetable world, that it is difficult in some species to

determine whether they are on the one side or the other. "Several of

them, however," says Mr. Gosse, "if viewed with a lens under water while

in a living state, display vigorous currents constantly pouring forth

from certain orifices; and we necessarily infer that the water thus

ejected must be constantly taken in through some other channel. On

tearing the mass open, we see that the whole substance is perforated in

all directions by irregular canals, leading into each other, of which

some are slender, and communicate with the surface by minute but

numerous pores, and others are wide, and open by ample orifices; through

the former the water is admitted, through the latter it is ejected." It

is not to be denied, however, that these beings constitute, in spite of

investigations of modern naturalists, a group still somewhat

problematical, and still very imperfectly known as regards their

internal organization.

Sponges are masses of a light elastic tissue, which is, at the same

time, resistant, full of air-cells, and with much varied exterior

arrangements. Nearly three hundred species are known, the different

appearances of which have been characterised by names more or less

singular. There is, for instance, the Feather Sponge, the Fan Sponge,

the Bell, the Lyre, the Trumpet, the Distaff, the Peacock Tail, and

Neptune's Glove.

There are river sponges and sea sponges.

The first are irregular and arenaceous masses, which pile themselves

upon plants and solid bodies immerged in fresh water. Such are the

_spongilles_, upon which anatomic and embryonic observations have very

frequently been made in relation to the group more immediately under

consideration.

The second is found in almost every sea; especially are they found in

the Mediterranean, the Red Sea, and the Mexican Gulf. Affecting warm and

quiet waters, they attach themselves to bold and rugged rocks at depths

ranging from five to twenty-five fathoms. They are erect, pendent, or

spreading, according to their form or position. Fig. 10, drawn from

Nature, represents a very remarkable form of sponge, which was fished up

in sixty fathoms.

The sponge is very common in the Mediterranean and round the Grecian

Archipelago, and is known vulgarly under the name of the Marine

Mushroom, the Sailor's Nest, and the fine soft sponge of Syria. It is a

mass more or less rounded, covered with a mucous bed, glutinous above,

formed of a light elastic but resisting tissue full of gaps, and

riddled with air-cells. This tissue is formed of delicate flexible

fibres, uniting in all directions by anastomosis, but presenting

numerous pores, which are formed by what is termed osculation, having

irregular _conduits_ which connect them. In this tissue certain very

small solid bodies are discovered, named _spiculæ_. The _spiculæ_ are

siliceous or calcareous in their nature, varying according to the

species, and sometimes varying even in the same species. Some of these

resemble needles, others are pin-like, and others again resemble very

small stars.

[Illustration: Fig. 10. Spongia, half the natural size, attached to its

rocky bed.]

The physiological function of those tubes and orifices which present

themselves on all parts of the sponge has been interpreted in various

ways. Ellis, writing in 1765, supposes that they were the orifices of

the cells occupied by the polypi. In 1816, Lamarck still advocated this

opinion; and even now we find the observer, whose notes M. Frédol has

edited with so much judgment, asserting that "the inhabitants of the

sponge are a species of fleeting, transparent, gelatinous tube,

susceptible of extension and contraction; young polypes, as we may call

them, without consistence, without cilia; incipient polypes, in short,

of very simple but sufficient organization. The animalcule of the sponge

is a stomach, without arms, very simple, very elementary--in short, an

animal all stomach!"

This mode of considering the sponge is not conformable to the views of

the leaders of modern science, however. Mr. Milne Edwards, for instance,

in place of seeing in the sponge a collection of united beings, forming

as it were a colony, considers each to be an isolated being, an unique

individual. The innumerable canals by which the sponge is traversed,

according to that author, are at once the digestive organs and breathing

pores of the zoophyte. The vibratile cilia are necessary to the renewed

aeration of the water required as a respiratory fluid in the interior

canals of the sponge. The currents in these channels have one constant

direction. The water penetrates the sponge by numerous orifices of

minute dimensions and irregular disposition; it traverses channels in

the body of the zoophyte, which reunite somewhat like the root of a

plant, in order to constitute the trunk and increase its substance;

finally, the water makes its escape by special openings. According to

this view, the channels of the sponge have a kind of cumulative

physiology, performing the two functions of digestion and respiration.

The rapid currents of aerated water which traverse them lead into them

the substances necessary to the nourishment of these strange creatures,

rejecting all excremental matter. At the same time, the walls of these

canals present a large absorbing surface which separates the oxygen with

which the water is charged, and disengages the carbonic acid which

results from respiration.

Sponges contain true eggs, from which embryo polyps are produced; these

have not cilia at first. In the interior of these eggs the contractile

cellules have their birth; then the spiculæ; and when they are finally

covered with the vibratile cilia, aided by them these larvæ of ovoid

form swim, or rather glide, through the water. The species of infusoria

born of the sponge resemble the larvæ of various polypes at the moment

they issue from the egg. "They soon attach themselves to some foreign

body," says Mr. Milne Edwards, "and become henceforth immovable; no

longer giving signs either of sensibility or of contractibility, while

in their enlargement they are completely transformed. The gelatinous

substance of their bodies is channeled and riddled with holes--the

fibrous framework is completed--the sponge is formed."

We may add, however, that other zoologists, and among them MM. Paul

Gervais and Van Beneden, take a different view of the development of the

sponges, and Dr. Johnston omits them altogether from his great work on

"British Zoophytes." "If they are not the production of polypi," he

says, "the zoologist who retains them in his province must contend that

they are individually animals, an opinion to which I cannot assent,

seeing that they have no animal structure or individual organs, and

exhibit not one function usually supposed to be characteristic of the

animal kingdom." Gervais and Van Beneden consider, as Milne Edwards

does, that the embryos are at first movable, then fixed, many of them

uniting together, and melting, as it were, into one common colony, which

become a sponge, such as we see it. An isolated embryo might also, by

throwing out germs, produce a similar colony, which would thus become a

product of agamous generation. Thus it appears that Science is far from

being settled in its views as to the organization and development of

these obscure and complex formations; nor is it more advanced in its

knowledge of the duration of life and the quickness of growth in

sponges. It is agreed, however, on one point--namely, that the

sponge-fisher may return to the same fishing-ground after three years

from the last fishing. At the present time sponge-fishing takes place

principally in the Grecian Archipelago and the Syrian _littoral_. The

Greeks and Syrians sell the product of their fishing to the Western

nations, and the trade has been immensely extended in recent times, when

the sponge has become an almost necessary adjunct of the toilet as well

as the stable, and in other cleansing operations.

Fishing usually commences towards the beginning of June on the coast of

Syria, and finishes at the end of October. But the months of July and

August are peculiarly favourable to the sponge harvest, if we may use

the term. Latakia furnishes about ten boats to the fishery, Batroun

twenty, Tripoli twenty-five to thirty, Kalki fifty, Simi about a hundred

and seventy to a hundred and eighty, and Kalminos more than two hundred.

The operations of one of these boats fishing for sponges on the Syrian

coast is represented in Plate II.

The boat's crew consists of four or five men, who scatter themselves

along the coast for two or three miles in search of sponges under the

cliffs and ledges of rock. Sponges of inferior quality are gathered in

shallow waters. The finer kinds are found only at a depth of from twelve

to twenty fathoms. The first are fished for with three-toothed harpoons,

by the aid of which they are torn from their native rock; but not

without deteriorating them more or less. The finer kinds of sponges, on

the other hand, are collected by divers aided by a knife; they are

carefully detached. Thus the price of a sponge brought up by diving is

much more considerable than that of a harpooned sponge. Among divers,

those of Kalminos and of Psara are particularly renowned. They will

descend to the depth of twenty-five fathoms, remain down a shorter time

than the Syrian divers, and yet bring up a more abundant harvest. The

fishing of the Archipelago furnishes few fine sponges to commerce, but a

great quantity of very common ones. The Syrian fisheries furnish many of

the finer kinds, which find a ready market in France; they are of medium

size. On the other hand, those which are furnished from the Barbary

coast are of great dimensions, of a very fine tissue, and much sought

for in England. On the Bahama banks, and in the Gulf of Mexico, the

sponges grow in water of small depth. The fishermen, Spanish, American,

and English, sink a long mast or perch into the water moored near the

boat, down which they drop upon the sponges; by this means they are

easily gathered.

[Illustration: Plate II.--Sponge Fishing on the Coast of Syria.]

In the Red Sea, the Arabs fish for sponges by diving, their produce

being either sold to the English at Aden or sent to Egypt.

Sponge-fishing is carried on at various other stations in the

Mediterranean, but without any intelligent direction, and in consequence

it is effected without any conservative foresight. At the same time,

however, the trade in this product goes on increasing. But it is only

a question of time when the trade shall cease; the demand which every

year clears the submarine fields of these zoophytes causes such

destruction that their reproduction will soon cease to be equal to the

demand.

In order to prevent this troublesome result, it is very desirable that

the several species of sponges should be naturalized on the French and

Algerian coast, and the cultivation and reproduction of the zoophyte

protected. For this purpose, the rocky coasts of the Mediterranean, from

Cape Cruz to Nice, and round the islands of Corsica and Hyères, in the

Algerian waters, and even some of the salt lakes of the departments near

the Mediterranean, might be utilized. The whole of the Italian littoral

would also be available under the new régime for this purpose.

M. Lamiral considered that the composition of the water of the

Mediterranean being thought the same on the coast of France, of Algeria,

and on the Syrian coast, that the difference of temperature between the

two latitudes--especially at the depth where the sponges flourish

most--would not interfere with the existence of these robust zoophytes,

and that their acclimatization on the coasts of France and Algeria would

be a certain success. He remarked, moreover, that the more the sponges

advanced towards the north, the finer and compacter their tissues

became; and he argued from this fact, that a considerable improvement in

the quality would result from the experiment.

The only difficulty, then, would consist in the transplanting sponges

from Syrian waters to the coasts of France and Algeria. A submarine

boat, such as M. Lamiral makes use of for operations conducted in deep

water, would, according to this naturalist, give every facility for

collecting sponges for the purpose. This boat can descend to great

depths, and its crew can dwell there a considerable time, for it is

continually fed with fresh air from above, which is conveyed by an

air-pump and tube into the interior of the boat, so that the men could

readily select such individuals as were suited for acclimatizing;

removing the blocks of rock along with them, either by placing them in

cases pierced with holes, or by towing them to their new abode.

Everything seems to promise that in the following year the zoophytes

would begin to multiply in their new country.

The larvæ might also be collected in the months of April and May, as

they separate from the parent sponge, and be transplanted to favourable

localities. At the end of three years, when these true submarine fields

would be ripe for harvesting, they could be put in train for methodical

collection by means of diving boats.

The toilet sponge is an article which produces a high price, often as

much as forty shillings the pound for very choice specimens, a price

which few commercial products attain, which prohibits its use, in short,

to all but the wealthy. It is, therefore, very desirable to carry out

the submarine enterprise of M. Lamiral. With the assistance of the

Acclimatization Society of Paris, some experiments have already been

made in this direction--so far without any satisfactory results, it is

true, but everything indicates that by perseverance we shall see the

enterprise crowned by the success it merits.

Such specimens as now reach our ports are chiefly distinguished by their

appearance, quality, and origin.

The fine soft Syrian sponge is distinguished by its lightness, its fine

flaxen colour, its form, which is that of a cup, its surface convex,

voluted, pierced with innumerable small orifices, the concave part of

which presents canals of much greater diameter, which are prolonged to

the exterior surface in such a manner that the summit is nearly always

pierced throughout in many places. This sponge is sometimes blanched by

the aid of caustic substances, acids, or alkalies; but this preparation

shortens its duration and changes its colour. This sponge is specially

employed for the toilet, and its price is high. Those which are

round-shaped, large, and soft, sometimes produce as much as five or six

pounds.

The _Fine Sponge of the Archipelago_ is scarcely distinguishable from

that of Syria, either before or after being cleansed; nevertheless, it

is weightier, its texture is not so fine, and the holes with which it is

pierced are at once larger and less in number. It is nearly of the same

country as the former, in fact, the fishing extending along the Syrian

coast as well as the littoral of Barbary and the Archipelago.

The _Fine Hard Sponge_, called Greek, is less sought for than either of

the preceding; it is useful for domestic and for certain industrial

purposes. Its mass is irregular, its colour fauve; it is hard and

compact, and pierced with small holes.

The _White Sponge of Syria_, called Venetian, is esteemed for its

lightness, the regularity of its form, and its solidity. In its rough

state it is brown in colour, of a fine texture, compact and firm.

Purified, it becomes flaxen and of a looser texture. The orifice of the

great channels which traverse it are edged with rough and bristly hairs.

[Illustration: (From Dr. Grant.)

Fig. 11. _Spongia oculata_, showing the orifices and currents outwards.

2. Anastomosing horny substance of _Spongia communis_. 3. Siliceous

spiculum of _S. papillaris_. 4. Of _S. cineria_. 5. _S. panicea_. 6.

Calcareous spiculum of _S. compressa_. 7. Transverse section of a canal

of _S. papillaris_, showing the structure of the ova passing along the

canal. 8. Ovum of _S. panicea_ seen laterally--the ciliæ anterior. 9.

The same seen on the end, with a circle produced by the ciliary action.

10. Young _Spongia papillaris_.]

The _Brown Barbary Sponge_, called the Marseillaise, when first taken

out of the water, presents itself as an elongated flattened body,

gelatinous, round in shape, and charged with blackish mud. It is then

hard, heavy, coarse, but compact, and of a reddish colour. By a simple

washing in water it becomes round, still remaining heavy and reddish. It

presents many gaps, the intervals of which are occupied by a sinuous and

tenacious network. It is valuable for domestic use, because of the

facility with which it absorbs water, and its great strength.

Other sorts of sponges are very abundant. The _Blonde Sponge_ of the

Archipelago, often confounded with the Venetian; the _Hard Barbary

Sponge_, called Gelina, which only comes by accident into France; the

_Salonica Sponge_ is of middling quality; finally, the _Bahama Sponge_,

from the Antilles, is wanting in flexibility and a little hard, and so

is sold at a low price, having few useful properties to recommend it.

Many species of _Spongia_ are described as inhabiting British seas, but

none of any commercial value. Regarding them as apolypiferous zoophytes,

Dr. Grant has pointed out certain principles of analysis on which they

may be grouped, according to the arrangement of the horny fibres, the

calcareous and siliceous spiculæ, and the distribution and formation of

their pores and orifices.

I. GROUPS OF WHICH THE CONSTITUENT STRUCTURE IS KNOWN.

_Spongia._--Mass soft, elastic, more or less irregular in shape, very

porous, traversed by many tortuous canals, which terminate at the

surface in distinct orifices. Substance of the skeleton cartilaginous,

fibres anastomosed in all directions, without any earthy

spicula.--Example, _S. communis_ (Fig. 11 [2]).

_Calcispongia_ (Blainville).--Mass rigid or slightly elastic, of

irregular form, porous, traversed by irregular canals, which terminate

on the surface in distinct orifices; skeleton cartilaginous, fibres

strengthened by calcareous spicula, often tri-radiate.--Example, _S.

compressa_ (Fig. 11 [6]).

_Halispongia_ (Blainville).--Mass more or less rigid or friable,

irregular, porous, traversed by tortuous irregular canals, which

terminate at the surface in distinct orifices; substance cartilaginous,

fibres strengthened by siliceous spicula, generally fusiform or

cylindrical.--Example, _S. papillaris_ (Grant) (Fig. 11 [3]).

_Spongilla_ (Lamarck).--Mass more or less rigid or friable, irregular,

porous, but not furnished with regular orifices or internal

canals.--Example, _S. fluviatalis_ (Linn.).

II. GROUPS DEPENDING ON CHARACTERS OF SURFACE OR GENERAL FIGURE.

_Geodia_ (Lamarck).--Fleshy mass, tuberous, irregular, hollow within,

externally incrusted by a porous envelope, which bears a series of

orifices in a small tubercular space.--Example, _G. gibberosa_

(Schmeiger).

_Coeloptychium_ (Goldfuss).--Mass fixed, pedicled, the upper part

expanded, agariciform, concave, and radiato-porose above, flat and

radiato-sulcate below; substance fibrous.--Example, _C. agarisidioideum_

(Goldfuss). Fossils from the chalk of Westphalia.

_Siphonia_ (Parkinson).--Mass polymorphous, free or fixed, ramose or

simple, concave or fistulous above, porous at the surface, and

penetrated by anastomosing canals, which terminate in sub-radiating

orifices within the cup.

_Myrmecium_ (Goldfuss).--Mass sub-globular, sessile, of a close fibrous

texture, forming ramified canals which radiate from the base to the

circumference. Summit with a central pit.

_Scyphia_ (Oken).--Mass cylindrical, simple, or branched, fistulous,

ending in a large rounded pit, and composed entirely of a reticulated

tissue.

_Eudea_ (Lamouroux).--Mass filiform, attenuated, sub-pedicellate at one

end, enlarged and rounded at the other, with a large terminal pit;

surface reticulated by irregular lacunæ, minutely porous.

_Halirrhoa_ (Lamouroux).--Mass turbinated, nearly regular, circular, or

lobate; surface porous; a large central pit on the upper face.

_Happalimus_ (Lamouroux).--Mass fungiform, pedicellate below, expanding

conically, with a central pit above; surface porous and irregularly

excavated.

_Cnemidium_ (Goldfuss).--Mass turbinate, sessile, composed of close

fibres and horizontal canals, diverging from the centre to the

circumference; a central pit on the upper surface, cariose in the

exterior and radiate at the margin.

_Ierea_ (Lamouroux).--Mass ovoid, sub-pedicellate, finely porous;

pierced on the upper part by many orifices, the terminations of the

internal tubes.

_Tethium_ (Lamarck).--Mass sub-globose, tuberose, composed of a cariose

firm substance, strengthened by abundance of siliciary spicula,

fasciculated, and diverging from the centre to the circumference.

RHIZOPODA.

Gervais and Van Beneden include under the name of _Rhizopods_, or

_foot-rooted_ animals (so called from ριξα,, _root_; πους,

ποδος, _footed animals_), those of the simplest organization, which

may be characterised by the absence of distinct digestive cavities, and

the presence of vibratile cilia, as well as by the soft parts of their

tissues. This tissue emits prolongations or filaments which admit of

easy extension, sometimes simple, sometimes branching. Occasionally we

see these branching filaments withdraw themselves towards the mass of

the body, disappear, and gradually melt into its substance in such a

manner that the individual seems to absorb and devour itself. If, in

exceptional cases, some of the superior animals, as the wolf, devour

each other, the rhizopods go much farther: they devour themselves, so

to speak!

The rhizopods are found both in fresh and salt water. They live, as

parasites, on the body of worms and other articulated animals. The class

is divided into many orders. We shall speak here only of three, namely,

the _Amoebæ_, _Foraminifera_, and _Noctiluca_.

AMOEBÆ.

In nearly all ancient animal and vegetable infusions, not quite

putrid--upon all oozy beds covering bodies which have remained for some

time in fresh or sea water--we find the singular beings which belong to

this order. They are the simplest organisms in creation, being reduced

to a mere drop of living matter. Their bodies are formed of a gelatinous

substance, without appreciable organization. The quantity of matter

which forms them is so infinitesimal, that it becomes incredibly

diaphanous, and so transparent that the eye, armed with the microscope,

traverses it in all directions, so that it is necessary to modify the

nature of the liquid in which it is held in suspension, and introduce

the phenomenon of refraction in order to observe them.

It would be difficult to say exactly what is the form these creatures

assume. They frequently have the appearance of small rounded masses,

like drops of water; but, whatever their form may be, it is always so

unstable, that it changes, so to speak, every moment, so that it is

found impossible to make a drawing from the model under the

microscope--the design must be finished by an appeal to memory. This

instability is the characteristic manifestation of life in the _Amoebæ_,

which are naked beings, without apparent organization; in fact, they

occupy the first step in the scale of creation.

The transparent immovable drop under consideration emits an expansion,

and a lobe of a vitreous appearance upon its circumference, which,

gliding like a drop of oil upon the object-glass of the microscope,

begins by fixing itself to it as a supporting point, afterwards slowly

attracting to itself the whole mass, and thus gradually increasing its

bulk under the observer's eye.

The _Amoebæ_, according to their dimensions and degree of development,

successively emit a greater or smaller number of lobes, none of which

are precisely alike, but, after having appeared for an instant, each

successively re-enters into the common mass, with which it becomes

completely incorporated. Variable in their respective forms, these lobes

present appearances quite different in the several genera. They are more

or less lengthy, more or less fringed, and often branching; sometimes

they are filiform, sprouting in all directions over the animal mass,

which rolls in the liquid like the husk of a small chestnut.

If we ask how these animals are nourished, in which no digestive

apparatus can be distinguished, the question is difficult to answer. It

is thought that they are nourished by simple absorption, and by

absorption only. In the interior of the gelatinous mass which

constitutes the animals, however, granules and microscopic portions of

vegetables are frequently discovered. "We can conceive," says Dujardin,

"how these objects have penetrated to the interior, if we remark, on the

one hand, that in creeping on the surface of the glass, to which they

adhere very exactly, the _Amœbæ_ can be made to receive, by pressure,

foreign substances into their own bodies, by means of the alternate

contraction and extension of the various parts natural to them, and, on

the other hand, that the gelatinous mass is susceptible of spontaneous

depressions--here and there near to or even at the surface of the

spherical cavities, which successively contract themselves and disappear

in connection with the strange body which they have absorbed."

The _Amoebæ_ are often observed to be tinted red or green; this arises

from the special colouring matter which has been absorbed into its mass.

The question arises, How do these creatures, so simple in their

organization, propagate their species?

We believe that they are chiefly multiplied by parting with a lobe,

which, in certain conditions, is enabled to live an independent

existence, and develop itself, thus forming a new individual. This is

what naturalists term generation by division--_fissiparism_ or

_fission_. The absence of a nutritive and reproductive apparatus in the

_Amoebæ_, and the want of stability in their forms, explain how nearly

impossible it is to characterise as species the numerous individuals

daily met with in infusions of organic matter in stagnant water. In

order to distinguish some of the groups, Dujardin bases his descriptions

upon their size and the general form into which they expand.

We shall be able to form some idea of the appearance of these beings,

rendered mysterious by their very simplicity, by throwing a glance upon

the two accompanying figures (Figs. 12 and 13), borrowed from the Atlas

of Dujardin's great work, "Les Zoophytes Infusoires," which we shall

have occasion to quote more than once.

We have said that the _Amœbæ_ change their form every few moments under

the eyes of the observer. Fig. 13 represents the changes of form through

which they pass, according to Dujardin, when examined under the

microscope.

[Illustration: Fig. 12. Amoebæ princeps (Ehrenberg), magnified 100

times.]

[Illustration: Fig. 13. Various forms of Amoebæ diffluens (Müller),

magnified 400 times.]

Dujardin points out very clearly the identity of structure between

organisms like _Amoebæ_ and such forms as _Difflugia_ and _Arcella_. All

these creatures are without trace of mouth or digestive cavity, and the

entire body is a single cell, or aggregation of cells, which receive

their nutriment by absorption; for, although the creatures have neither

mouth nor stomach, yet, according to Professor Kölliker, they take in

solid nutriment, and reject what is indigestible. When in its progress

through the water one of these minute organisms approaches one of the

equally minute Algæ, from which it draws nourishment, it seizes the

plant with its tentacular filaments, which it gradually encloses on all

sides; the filaments, to all appearance, becoming more or less shortened

in the process. In this way the captive is brought close to the surface

of the body; a cavity is thus formed, in which the prey is lodged, which

closes round it on all sides. In this situation it is gradually drawn

towards the centre, and passes at last entirely into the mass. The

engulfed morsel is gradually dissolved and digested.

FORAMINIFERA.

There is nothing small in Nature. The idea of littleness or greatness is

a human conception--a comparison which is suggested by the dimensions of

his own organs. Nature, on the other hand, compensates smallness by

numbers. The result produced by the bones of some large animals is also

accomplished by the accumulated spoils of millions of animalcules. The

history of the Foraminifera is a striking example of this great truth.

What, then, is a Foraminifer? It is a very small zoophyte, a shell

nearly invisible to the naked eye; for, in general, its dimensions

rarely exceed the two hundredth part of an inch; in short, it is

strictly microscopic. Examine under a microscope the sand of the ocean,

and it will be found that one-half of it consists of the débris of

shells, of various but well-defined forms, each habitually pierced with

a number of holes. To this they are indebted for their name

Foraminifera, from _foramen_, a hole. With these microscopic animalcules

Nature has worked wonders in geological times; nor have the wonders

ceased in our days.

Many beds of the terrestrial crust consist entirely of the remains of

Foraminifera. In the most remote ages in the history of our planet,

these zoophytes must have lived in innumerable swarms in the seas of the

period; they buried themselves in the bottoms of the seas, and their

shells, heaped up during many ages, have finished by forming hills of

great thickness and extent. We may say, to give an example, that during

the Carboniferous period, a single species of these zoophytes has

formed, in Russia alone, enormous beds of calcareous rock. Many beds of

cretaceous formation are, in great part, composed of Foraminifera, and

they exist in immense numbers in the white chalk which covers and forms

the vast mountains ranging from Champagne, in France, nearly to the

centre of England.

But it is to the Tertiary formation that these zoophytes have

contributed the most enormous deposits. The greater part of the Egyptian

pyramids is only an aggregation of _Nummulites_ inserted in the syenite.

A prodigious number of Foraminifera present themselves in the tertiary

deposits of the Gironde, of Italy, and of Austria. The chalk so abundant

in the basin of Paris is almost entirely composed of Foraminifera. The

remains of these creatures are so abundant in the Paris chalk, that M.

d'Orbigny found upwards of fifty-eight thousand in a small block,

scarcely exceeding a cubic inch of chalk, from the quarries of

Chantilly. This fact, according to this author, implies the existence of

three thousand millions of these zoophytes in the cubic mètre

(thirty-nine inches square and a small fraction) of rock! As the chalk

from these quarries has served to build Paris, as well as the towns and

villages of the neighbouring departments, it may be said that Paris, and

other great centres of population which surround it, are built with the

shells of these microscopic animals.

The sand of the littoral of all existing seas is so full of these minute

but elegant shells, that it is often half composed of them. Ehrenberg,

the celebrated German microscopist, was recently invited by the Prussian

government to assist in tracing the robbery of a special case of wine.

It had been repacked in littoral sand only found in an ancient sea-board

in Germany. The criminal was thus detected. M. d'Orbigny found in three

grammes (forty-six grains troy) of sand from the Antilles, four hundred

and forty thousand shells of Foraminifera. Bianchi found in thirty

grammes (four hundred and sixty-seven grains) from the Adriatic, six

thousand of these shells. If we calculate the proportion of these beings

contained in a cubic mètre alone of sea-sand, we reach a figure which

passes all conception. What would this be if we could extend the

calculation to the immensity of surface covered by the waves which

surround the globe?

M. d'Orbigny has satisfied himself, by microscopic examination of sands

from all parts of the globe, that it is the débris of Foraminifera which

form, in all existing seas, those enormous deposits which raise banks,

obstruct the navigation in gulfs and straits, and fill up ports, as may

be seen in the port of Alexandria. In common with the corals and

madrepores, the Foraminifera are the great agents in forming the isles

which surge up under our eyes from the bosom of the ocean in the warmer

regions of the globe. Thus shells, scarcely appreciable to the sight,

suffice by their accumulations to fill up seas, while performing a very

considerable part in the great operations of Nature, although it may not

be apparent to us.

Our exact knowledge of the Foraminifera is of very recent date. Great

numbers of minute particles, of regular and symmetrical form, were long

distinguished on the sands of the sea shore. These corpuscular atoms

early attracted the attention of observers. But with the discovery of

the microscope, these small elegant shells, which were among the

curiosities revealed by the instrument, assumed immense importance. We

have stated that these corpuscles are nothing but the shell or solid

framework of a crowd of marine animalculæ: we may then consider them as

living species analogous to the Ammonites and Nautilus of geological

times. Linnæus has placed them in this last genus, which would include,

according to that author, all the multilocular shells. In 1804, Lamarck

classed them among the molluscous cephalopods. But Alcide d'Orbigny, who

has devoted long years to study and observation, and may be considered

the great historian of the Foraminifera, makes it appear that this mode

of classification was inexact. Dujardin separated them altogether from

the class of mollusks, and showed that they ought to be consigned to an

inferior class of animals. These minute creatures, in short, are

deficient in the true appendages analogous to feet, which exist in the

higher mollusks. They simply possess filamentous expansions, very

variable in their form.

We have stated that the Foraminifera are of microscopic dimensions. With

some trifling exceptions, this is generally true; but there exist a

number of species which are visible to the naked eye. The Foraminifers

found in the nummulite formation of Tremsted, in Bavaria, between Munich

and Saltzberg, are still larger, being nearly double the size of the

nummulite of the Pyramids; in short, they are the giants of this tribe

of animals.

After these remarks, we may venture to give some idea of the structure

and classification of these beings, whose part in the work of creation

has, in former times, been so considerable.

The bodies of the Foraminifera are formed of a gelatinous substance,

sometimes entire and round, sometimes divided into segments, which can

be placed upon a line, simple or alternate, wound up into a spiral form

or rolled round its axis, like a ball. A testaceous envelope, modelled

upon the segments, follows the various modifications of form, and

protects the body in all its parts. From the extremity of the last

segment of one or many openings of the shell, or of the numerous pores,

issue certain long and slender filaments, more or less numerous, which

are divided and subdivided over their whole length, like the spreading

branches of a tree. They can attach themselves to external bodies with

force enough to determine the progression of the animal. Being formed of

transparent non-colouring matter, they may be said to be mere

expansions, which vary in form and length according to the conditions of

the ambient medium. The filaments have also very variable positions:

sometimes they form an unique and retractile band, issuing from a single

opening; sometimes they project themselves across from numerous little

pores in the shell, which covers the last segment of the animal. These

pores, or openings, give the name to the creatures under consideration.

In conclusion, the filaments, contractile and variable in their form,

which constitute the feet and arms of these little creatures, appear to

have something electric in them: it is stated that the Infusoria are at

once paralysed in their motions when brought in contact with the minute

arms of the Foraminifera. "It is probably by this means," says M.

Frédol, "that these creatures succeed in catching their prey. Is it not

worthy of remark that these beings, however small their size and slight

their form, are unpitying flesh-eaters? The smallest, the weakest, and

the most microscopic animal in existence thus becomes, by means of a

homœopathic dose of poison, a most formidable destroyer."

Another singular observation on these little filaments or arms we owe to

Dujardin. This naturalist observed that, when a _miliola_ attempted to

climb up the walls or sides of a vase, it could improvise, as it were,

on the instant, and at the expense of its own substance, a provisional

foot, which stretched itself out rapidly and performed all the functions

of a permanent member. The occasion served, this temporary foot seemed

once more to return to the common mass, and was absorbed into the body.

It would thus appear that with these minute creatures the presence of a

necessity gives the power to create an organ by the mere will of the

creature, while man, with all his genius, cannot manufacture a hair. To

the present day, however, we have not been able to discover any organ of

nutrition in the Foraminifera; they have no stomach, properly so called,

but Nature has gifted them with a peculiar tissue, at once gelatinous

and contractile, and essentially simulative, which probably serves the

same purpose.

We have already said that the shells of these minute zoophytes vary much

in form. They are generally many-chambered, each chamber communicating

by pores in the walls; the different gelatinous parts of the animalcules

are, in this manner, placed in continual communication with each other.

Alcide d'Orbigny, to whom we owe almost all that is known of the class,

has distributed them into six families, making the form of the shell the

basis of their arrangement. These six families include sixty genera, and

more than sixteen hundred species, the families being as follows:--

I. Monostega.--Animals consisting of a single segment. Shell of a single

chamber.

II. Stichostega.--Animal in segments, arranged in a single line. Shell

in chambers, superimposed linearly on a straight or curved axis.

III. Helicostega.--Animal in segments, spirally arranged. Chambers piled

or superimposed on one axis, forming a spiral erection. In Fig. 21 we

have a horizontal section of _Faujasina_, in which the spiral

convolutions are visible on the truncated half of the shell.

IV. Entomostega.--Animal composed of alternating segments forming a

spiral. Chambers superimposed on two alternating axes, also forming a

spiral.

V. Enallostega.--Animal formed of alternate segments. Non-spiral

chambers disposed alternately along two or three axes, also non-spiral.

VI. Agathistega.--Animal formed of segments wound round an axis.

Chambers formed round a common axis, each investing half the

circumference.

The simplest form of Foraminifera is illustrated by Fig. 14 (_Orbulina

universa_), which is a small spherical shell, having a lateral aperture,

the interior of which has been occupied by the living jelly, to which

the shell owes its existence. In the second order, the shell (Fig. 15),

_Dentalina communis_, advances beyond this simple type by a process of

linear budding, the first cell being spherical, with an opening through

which a second segment is formed, generally a little larger than the

first. This new growth is successively followed by others developed in

the same way, until the organism attains its maturity, when it exhibits

a series of cells arranged end on end, in a slightly curved line.

In the next group the gemmation takes a spiral bias, producing the

nautilus shape which misled the earlier naturalists. In some cases all

the convolutions are visible, as in _Operculina_ (Fig. 16). In others,

the external convolute conceals those previously formed, as in

_Nummulitis lenticularis_ (Fig. 17), _Cassidulina_ (Fig. 18),

_Textilaria_ (Fig. 19), and _Alveolina oblonga_, d'Orbigny (Fig. 25),

the latter forming part of the eocene formation in the quartz and

greystone rocks of the neighbourhood of Paris; one figure representing

the shell entire, and the other a vertical section, while the small

figure between represents it in its natural size.

[Illustration: Fig. 14. Orbulina universa.]

[Illustration: Fig. 15. Dentalina communis.]

[Illustration: Fig. 16. Operculina.]

[Illustration: Fig. 17. Nummulitis lenticularis.]

[Illustration: Fig. 18. Cassidulina.]

[Illustration: Fig. 19. Textilaria.]

[Illustration: Fig. 20. Spiroloculina.]

In the fourth group the shell is spiral, with the chamber equilateral,

with a larger and smaller side, the position being alternately reversed

as the segments are multiplied, as in _Cassidulina_ (Fig. 18). In the

succeeding group the new segments are arranged alternately on opposite

sides of the central line, as in _Textilaria_ (Fig. 19), thus forming

two alternating non-spiral parallel segments, each connected by a single

orifice.

The sixth family differ entirely in appearance and structure from the

other Foraminifera. They are more opaque than the other orders, having a

resemblance to white porcelain, which presents a rich amber-brown hue

when viewed by transmitted light. They are more or less oblong, each new

segment being nearly equal to the entire length of the shell, so that

the terminal orifice presents itself alternately at its opposite

extremities, sometimes in one uniform plane, as in _Spiroloculina_ (Fig.

20), and _Faujasina_ (Fig. 21). At other times each new segment, instead

of being exactly opposite each other, is a little on one side.

[Illustration: Fig. 21. Faujasina.]

Professor Williamson has shown that the shell enclosing each new segment

is at first very thin; but as additional calcareous chambers are formed,

each addition not only encases the new gemmation of the soft animal, but

extends over all the exterior of the previously formed shell. The exact

manner in which this is accomplished is doubtful; but the Professor

thinks it probable that the soft animal has the power of diffusing its

substance over the shell, and thus depositing upon its surface

additional layers of calcareous matter.

The fossil Foraminifera are chiefly distinguished from recent and

existing species by the size of the former. While the living forms range

from one-fourth to the one-hundredth part of an inch, the tertiary

strata abound in examples of _Nummulites_ varying from the eighth of an

inch to the size of half-a-crown. The engraving is a drawing from

Nature, by MM. d'Archaic and Haime, of a piece of nummulitic rock, of

Nousse, in the Landes, in which a great variety of sizes and forms are

exhibited.

The Nummulina belong to the third family, or Helicostega, in which the

outer convolutions completely embrace the earlier-formed ones. Hence it

is only by making microscopic sections, or thin slices, that their

structure can be fully seen. When such a section is carried horizontally

through the centre of the shell, the segments present a spiral

arrangement, which, like the convolutions, are remarkable for their

small size, and consequent great number.

[Illustration: Fig. 22. Nummulites Rouaulti (d'Archaic and J. Haime).]

[Illustration: Fig. 23. Siderolites calcitrapoides (Lamarck). Natural

size and magnified.]

With respect to the distribution of the Foraminifera according to

geological periods, we may briefly state that they have been found in

every formation from the Silurian to the Tertiary. The species, at first

very simple in their forms, begin to appear in increasing numbers in the

carboniferous formations. They become more numerous, and, at the same

time, more complex in their forms, in the Cretaceous period; they are

still more diversified, and appear to have multiplied much more rapidly

in the Tertiary period, where they attain the maximum of their numerical

development. In the celebrated quarries of St. Peter, at Maestrecht, the

_Siderolites calcitrapoides_ of Lamarck are found in the upper chalk

(Fig. 23). In the calcareous formation of Chaussy, in the Seine and Oise

district, and other parts of the Paris basin, the _Fabularia

discolithes_ (Fig. 24) of Defrance is found. Finally, the _Dactylopora

cylindracea_ of Lamarck (Fig. 26) is found in the eocene formation of

Valmondois and in the chalk of Grignon. At first, this little creature

was thought to be a polype; but d'Orbigny, in his "Prodrome de

Paleontologie," has placed it among the Foraminifera, thinking that it

appeared to occupy a place between the two classes.

[Illustration: Fig. 24. Fabularia discolithes (Defrance). Natural size

and magnified.]

[Illustration: Fig. 25. Alveolina oblonga (d'Orbigny). Natural size and

magnified.]

[Illustration: Fig. 26. Dactylopora cylindracea (Lamarck). Natural size

and magnified.]

The existing Foraminifera are by no means equally distributed in every

ocean. Some genera belong to warm countries, others to temperate and

cold climates. They are much more numerous, however, and much more

varied in their forms, in warm than in cold climates, and, we may add,

larger also, for Sir E. Belcher brought a recent species from Borneo

which measured two inches in diameter.

* * * * *

Before passing on to the study of the Infusoria, a few words may be

offered on the _Noctiluca_, a genus of animals usually referred to the

class ACALEPHÆ. One species only of this genus has been described, which

occurs occasionally on the English coast in prodigious numbers. It is a

small creature, scarcely the hundredth part of an inch in diameter,

according to Mr. Huxley (Fig. 27, _Noctiluca miliaris_). It was

discovered by M. Surriray, in 1810, who describes it as a spherical

gelatinous mass, scarcely bigger than a pin's head, with a long filiform

tentacular appendage, a mouth, an oesophagus, one or many stomachs, and

branching ovaries--thus exhibiting a certain complexity of organization.

De Blainville took the same view, and placed it among the _Diphydæ_. Van

Beneden and Doyère, on the other hand, deny its relation to the

_Acalephæ_, conceiving its organization to be much more simple: they

place it with the _Rhizopoda_. Quatrefages adopts the same view, denying

the existence of a true mouth or intestinal canal: he considers the

so-called stomachs as simple "vacuales," similar to those observed in

the Rhizopoda and Infusoria. Mr. Huxley, describing it in the "Journal

of Microscopical Science" (vol. iii.), says it has nearly the form of a

peach, a filiform tentacle, equal in length to the diameter of the body,

occupying the place where the stalk of the peach might be, which depends

from it, and exhibits slow wavy motions when the creature is in full

activity. "I have even seen a _noctiluca_," he adds, "appear to push

against obstacles with this tentacle."

[Illustration: Fig. 27. Noctiluca miliaris. Magnified.]

"The body," he continues, "is composed of a structureless and somewhat

dense external membrane, which is continued on to the tentacle. Beneath

this is a layer of granules, or rather of gelatinous membrane, through

whose substance minute granules are scattered without any very definite

arrangement; from hence arises a network of very delicate fibrils, whose

meshes are not more than one three-hundredth part of an inch in

diameter, which gradually pass internally--the reticulation becoming

more and more open--into coarser fibres, taking a convergent direction

towards the stomach and nucleus. All these fibres and fibrils are

covered with minute granules, which are usually larger towards the

centre."

Mr. Huxley is inclined to think, from all he has observed, that the

animal has a definite alimentary cavity, and that this cavity has an

excretory aperture distinct from the mouth.

Surriray discovered the _noctiluca_ while investigating the cause of

phosphorescence of sea water at Havre, where it was abundant in the

basins; sometimes in such abundance as to form a crust on the surface of

the water of considerable thickness. "This singular little creature,"

says M. Frédol, "offers here and there in its interior certain granules,

probably germs, and also luminous points, which appear and disappear

with great rapidity--the least agitation determining their lustre." The

_noctiluca_ are so abundant in the Mediterranean and in some parts of

the channel, that in a cubic foot of sea water, which has been rendered

phosphorescent by their presence, it is calculated that there exist

about twenty-five thousand.

INFUSORIA.

With the Infusoria we return to the domain of the infinitely little. Of

this very interesting group a large proportion are marine, and numerous

varieties of them are found in British seas. In their minuteness and

variety they almost baffle the attempts of naturalists to classify them.

The waters, both fresh and salt, are inhabited by legions of active,

ever-moving beings, of dimensions so small as to be inappreciable to the

naked eye; these minute creatures are disseminated by millions and

thousands of millions in the great deep, and all knowledge of them would

have escaped us, as they escaped the knowledge of the ancients, but for

the discovery of the microscope, the sixth sense of man, as it has been

happily expressed by the historian and poet Michelet. Another writer of

equally poetical mind, M. Frédol, tells us that "the infusorial

animalcules are so small that a drop of water may contain them in many

millions. They exist in all waters, the fresh as well as the salt, the

cold as well as the hot. The great rivers are continually discharging

them in vast quantities into the sea."

The Ganges transports them in the course of one year in masses equal to

six or eight times the size of the great pyramid of Egypt. Among these

animalcules, according to Ehrenberg, we may reckon seventy-one different

species.

The water collected in vases between the Philippine and the Marianne

Isles at the depth of twenty-two thousand feet (making some allowance

for erroneous soundings), have yielded a hundred and sixteen species.

Near the Poles, where beings of higher organization could not exist, the

Infusoria are still met with in myriads; those which were observed in

the Antarctic Seas, during the voyages of Captain Sir James Ross, offer

a richness of organization, often accompanied by elegance of form, quite

unknown in more northern regions. In the residuum of the blocks of ice

floating about in latitude seventy-eight degrees ten minutes, nearly

fifty different species were found. Many of them had ovaries, according

to Ehrenberg, still green, which proved that they had struggled

successfully with the rigours of the climate in searching for food.

At a depth in the sea which exceeds the height of the loftiest mountain,

Humboldt asserts that each bed of water is animated by an innumerable

phalanx of inhabitants imperceptible to the human eye. These microscopic

creatures are, in short, the smallest and the most numerous creations in

Nature. They constitute with human beings one of the wheels of that very

complicated machine, the globe. They are in the rank and at the station

willed for them, as determined in the great First Thought. Suppress

these microscopic beings, and the world would be incomplete. It was

said, and wisely said, long, long ago, "there is nothing so small to the

view but that it may become great by reflection."

The Infusoria, in short, abound everywhere. We find their remains on the

loftiest mountain ridges, and in the profoundest depths of the sea. They

increase and multiply alike under the Equator, and towards the polar

regions. The seas, rivers, ponds--the flower vase which rests upon the

casement--even our tissues, and the fluids of our bodies--all contain

infusorial animalcules. Whole beds of strata, often many feet thick, and

covering a surface of considerable extent, are almost exclusively formed

of their accumulated débris. It is to the Infusoria that the mud of the

Nile and other fluviatile and lacustrine deposits owe their prodigious

fertility. To them also is due the red or green layer of colouring

matter found in ponds and tanks at certain seasons. When exposed to

great solar heat, in order to extract the salt, as it is in the vast

artificial basins hollowed out for the purpose in the salt marshes near

the sea-shore in the south of France, the salt water, when it reaches a

certain degree of concentration, acquires a fine rose colour, which is

due to the presence of innumerable masses of small Infusoria having a

reddish shell. Finally, let us add that the solid débris of certain

fossil Infusoria, of surprising minuteness, have formed the stone so

much used by workers in metal, which is known as _tripoli_.

The study of these creatures is intensely interesting to the naturalist,

the philosopher, the physician, and the general reader. They have had a

great part assigned to them in Nature, as is evident in the formation of

certain beds of rock of immense extent, in which the geologist traces

their action.

Our earliest knowledge of the Infusoria is traceable to the seventeenth

century; to the celebrated naturalist, Leuwenhoek, we are indebted for

their discovery. On the 24th of April, 1676, this observer saw for the

first time some infusorial animalcules. Fifty years later, Baker and

Trembley studied them anew. In 1752, Hill essayed the first attempt at

their classification. In 1764, Wiesberg gave them the name of Infusoria,

because he found them in such great abundance in animal and vegetable

_infusions_. Müller published a special book upon them.

From that time the Infusoria have been considered as forming a special

group among the radiate animals; afterwards, in the pages of Baer and of

De Blainville, we see in these creatures, so imperfect in appearance,

only the indeterminate prototype of other classes. But ideas changed

altogether respecting them when microscopes of great power, and armed

with achromatic lens, were employed in their study. Thanks to the

labours of Ehrenberg and Dujardin, we have arrived at a better

comprehension of the organization of these infinitely small beings.

Naturalists have established, with more exactness, the limits of the

zoological group to which they belong.

Some stagnant waters are so filled with Infusoria that it is only

necessary to dip at random into the liquid medium to procure them in

abundance. In other waters they form a bed, occupying the whole basin.

In general, it is necessary to search for them where the water is calm,

and occupied by vegetation of some kind, such as the _confervæ_, or

_lemna_, &c., in the marshes, and _ceramium_ if in the sea. Certain

Infusoria live not only in water, but also in places habitually moist,

as among tufts of mosses; in beds of _oscillaria_, on moist soil, or on

air-damp walls. Others live as parasites on the exterior or in the

interior of animals, such as _hydra_, _lombrics_, and _naïads_.

Quantities of them are found in the liquid excrements and other

products of certain organisms, and they have been noted even in women's

milk.

But, as their name indicates, it is in aqueous infusions, vegetable or

animal, that these animalcules abound. Armed with a microscope, the

reader may, with very little trouble, afford himself the pleasure of

studying these animals. It is only necessary to place some organic

débris--the white of an egg, or some grass, for example--in a vase with

a large mouth, filled with water, and expose it to the light and air.

Certain reagents, as phosphate of soda, the phosphates, nitrates, or

oxalates of ammonia, or carbonate of soda added to these infusions, will

singularly favour the development of Infusoria.

There are also some accidental infusions which seem to furnish these

microscopic beings in great abundance. Water which stagnates in garden

soil or in vegetable mould, in the watering-cart or in flower vases, is

filled with myriads of these beings.

* * * * *

So much for the medium in which they live, move, and have their being.

Let us pass on to their organization. We have already dwelt on their

extreme minuteness; their mean size is a fifth of a line or the sixtieth

part of an inch; the largest species scarcely reveal themselves to the

naked eye. They are generally colourless; some of them are,

nevertheless, green, blue, red, brown, and even blackish. Seen on the

object-glass of the microscope, they appear to be gelatinous,

transparent, and naked, or invested with an envelope more or less

resistant, which we shall designate after Dujardin by the term

_Sarcoda_, a substance which is homogeneous, diaphanous, elastic,

contractile, and, above all, destitute of every kind of organization.

They are usually ovoid or globular. Those most frequently met with, and

which attract the most attention from observers, are furnished with

_vibratile cilia_, which cover the whole body, acting as paddles. These

organs are evidently intended to propel the animal from one place to

another. At other times they appear to be employed in conveying food to

the mouth, if we may use the expression. Some Infusoria are without

these cilia, having only one or many very slender filaments, the

undulating movement of which suffices to determine their progression

through the liquid which surrounds them.

Authors who have written on the Infusoria have sometimes, like

Leuwenhoek, Ehrenberg, and Pouchet, attributed to them a very complex

structure. Others, like Müller, Cuvier, and Lamarck, have considered

them to be gifted with an organization extremely simple. We shall

probably find that the truth lies between these two extremes.

In the superior Infusoria, besides the granules, the interior globules,

vesicles full of liquid, vibratile cils, and a tegumentary system, more

or less complex, we find the substance which is called _Sarcoda_.

The digestive apparatus of the Infusoria has been the subject of

numerous observations, and has been provocative of very animated

discussions. In the inferior order of the class, which comprehends the

very smallest animalcules, it has not been found possible to observe the

organization of the digestive apparatus in a satisfactory manner. Some

writers think they have no mouth, what has been taken for that organ

being only hollow dimples on the surface of the body; others recognize

the existence of a buccal orifice, sometimes furnished with a solid

armature. As to the arrangements of the interior cavities in which

digestion takes place, we know nothing certain.

The digestive apparatus is better understood in the superior Infusoria,

called _ciliate_, namely, those provided with _vibratile cils_. These

cils seem to determine the currents of the liquid, leading the nutritive

corpuscles suspended in the water towards the entrance of the digestive

apparatus. They form, in some sort, the prehensile organs which seize

the aliment. The cils are, at the same time, the organs intended to

facilitate respiration; in short, these little whips playing upon the

water unceasingly round the Infusoria, is just the action required for

the absorption of the oxygen contained in the water. These cils, then,

serve at once for the propulsion of the animal, for its nutrition, and

for its respiration, presenting a remarkable example of cumulative

functions in physiology.

The corpuscles of nutritive substances directed towards the buccal

orifice by the vibratile cils soon disappear in the interior of the

animal. Availing himself of this fact and the transparency of the

animal, Herr Gleichen, a German physiologist of the last century,

conceived the happy idea of colouring the water which contained these

animalcules with a finely-powdered carmine; he traced the colouring

matter in the bodies of some of them. But it was reserved for Ehrenberg

to avail himself of the same artifice in order to study the internal

structure and mode of absorbing nutritive matter in these minute

creatures. This physiologist fed many groups of Infusoria, some of them

with water coloured with carmine, others with indigo and other

colouring matters. He saw, besides, some coloured globules, nearly

uniform in size, in different individuals of the same species. From this

he arrived at the conclusion that the colouring matter was deposited in

many of the surrounding dimples. Ehrenberg thought that each of these

dimples was a stomach, and that the introduction of the food into the

interior of these reservoirs, as well as the evacuations, were produced

by means of an intestine around which these stomachs are arranged. In

some cases he even thought he could distinguish the outlines of this

intestinal canal, and its connection with numbers of ampula or bladders.

Generalizing the conclusions drawn from his observations, in short, we

find that his class, Infusoria, embraced two very different forms of

animal life, which he divided into _Infusoria_, _Polygastrica_, and

_Rotifera_, the latter division including those known as Wheel

animalcules; the _Polygastrica_ being so called from his idea that the

typical forms possessed a number of stomachs. In some, Ehrenberg counted

four stomachs, an organization which brings these microscopic beings

into a strange kind of comparison with the ox and the goat. In others he

counted two stomachs.

Other observers were not slow in raising objections to these views.

Dujardin, especially, was much opposed to the batch of stomachs

attributed to these creatures by the German physiologist. He attempted

to establish the fact that the coloured globules which appeared in the

bodies of the Infusoria, while subjected to a regimen of carmine and

indigo, are not confined by a membrane; that is to say, they are not

contained in intestinal sacs. According to Milne Edwards, "they are a

species of basins, constituted," he says, "by the alimentary matter with

which each is gorged, united into a rounded pasty mass, where it could

no longer be dispersed, but would continue to advance, still preserving

its form. We have, in short, seen these spherules changing their places,

and passing one another in their progress from the mouth to the

intestinal canal. That they could not do this is evident, if many

stomachs were attached to the intestinal canal!"

This opinion, due to the patient and precise studies of Dujardin, has

been adopted by most naturalists of eminence. Besides, this learned

microscopist does not admit that there was in the sarcodic mass of

Infusoria any pre-existent cavity destined to receive the food. In a

word, he does not recognise any stomach whatever. This view of the

extreme simplicity of structure in the Infusoria has, however, met with

much opposition. To accord them neither four nor two stomachs, it is not

necessary to deprive them of the organ altogether. Meyen represents them

as having one great hollow stomach occupied by a pulpy matter, into

which the alimentary masses are successively absorbed. "All recent

observations," says Milne Edwards, "tend to establish the fact that the

digestive apparatus of the ciliate Infusoria consists of--first, a

mouth; second, of a pharyngeal canal, in which the food often assumes

the form of a _bolus_; third, of one great stomach with distinct walls,

and more or less distant from the common tegumentary membrane; fourth,

of an excretory orifice."

This mouth presents sensible differences both as to its position and

conformation, often occupying the bottom of a hollow, the edges of which

are furnished with well-developed _cilia_, the action of which attracts

the aliment; in short, the mouth is a sort of decoy at the bottom of a

simple pit, being at once contractile and prehensile, the interior part

being sometimes capable, according to Milne Edwards, of being turned

inside out in the form of a trumpet, while in a great many species it is

provided with a peculiar armature, consisting of a band of rigid

bristles disposed in the form of a bow-net, and susceptible of

dilatation and contraction, according to the wants of the animal. The

oesophagus, which is connected by means of the canal with the mouth, has

generally an oblique direction backwards, often terminating in a great

undivided stomach.

The reproduction of the Infusoria exhibits some very surprising

phenomena, while it offers another proof of the wonderful means Nature

employs for perpetuating the races of animals. They can be reproduced by

three different processes: 1. By _gemmation_, or budding, somewhat after

the manner of plants. 2. By sexual reproduction; for in these little

creatures it has recently been discovered that sexual differences exist.

3. By the spontaneous division of the animal into two individuals--a

process known to zoologists as _fissiparism_ or _fission_.

Among these three processes, that which appears best understood is the

last. The singular phenomenon of spontaneous division may be witnessed

by any one having patience to examine the creature long enough, isolated

from its innumerable companions, under the microscope. The oblong body

of the animal will soon be observed to contract at the middle, the

compression becoming more and more marked. The lower segment soon

begins to show a few vibratile cils, thus indicating the place which

will soon be a new mouth; the organ soon becomes more and more distinct,

and now the Infusoria literally cuts itself into two parts. We see, at

first, the fragment of glutinous substance fluttering on the edge of the

plate; the two halves then separate from each other very quickly, each

moiety having finally a perfect resemblance to the primitive animal.

This process is represented in Fig. 28, A and B being the adult, C the

same in course of separation, D after its completion. Assuredly this is

one of the most remarkable phenomena which the study of living beings

can present. "By this mode of propagation," says Dujardin, "an infusoria

is the half of the one which preceded it, the fourth of the parent of

that, the eighth of its grand-parent, and so on, if we can apply the

terms father or mother to animals which must see in its two halves the

grandfather himself by a new division again living in his four parts. We

might imagine such an infusoria to be an aliquot part of one like it,

which had lived years, and even ages before, and which by continued

subdivision into pairs might continue to live for ever by its successive

development."

[Illustration: Fig. 28. Propagation of an Infusoria by spontaneous

division.]

This mode of generation, however, enables us to comprehend the

miraculous fecundity of these beings. The process defies calculation, if

we wished to be precise. We may, however, arrive at a proximate estimate

of the number which may be derived from a single individual by this

process of fission. It has been found that at the end of a month two

_Stylonichiæ_ had a progeny of more than one million and forty-eight

thousand individuals, and that in a lapse of forty-two days a single

_Paramecium_ had produced more than one million three hundred and

sixty-four thousand forms like itself.

Life is spread over Nature in such abundance that the smallest infusoria

has its parasite a little smaller; these in their turn serving as "a

dwelling and pasture ground," to use Humboldt's words, for still smaller

animalcules, as represented in Fig. 29--_a_ being parasites in various

stages; _b_, the larger animalcule on which they have established

themselves.

[Illustration: Fig. 29. Paramecium aurelia and its Parasites.]

The prodigious number to which the calculation would reach, if we were

to add the other modes of propagation, viz., by germs and by budding, we

dare not mention: it would only be necessary to place a single germ in a

favourable condition for its development, in order to produce myriads of

these microscopic animalcules in a very few days.

We have seen three modes of reproduction in the Infusoria; it is

possible that a fourth mode exists, to which its partisans give the name

of _spontaneous generation_. According to their views, an infusoria can

be produced without egg-germ or pre-existent parent. It would be

sufficient to expose organic matter, animal or vegetable, to the action

of the air and water at a suitable temperature, in order to see this

matter organize itself, and form itself into living infusorial animals.

Such is the general enumeration of the question of spontaneous or

_heterogeneous_ generation, on which so much has been written in the

last ten years. The great expounders of the doctrine have been the two

French naturalists, MM. Pouchet and Joly. Their views have, however,

made little progress; they have, on the contrary, met with vigorous

opposition from the generality of French naturalists, and from most of

the members of the Académie des Sciences of Paris, who have raised their

voices against a doctrine which is contrary to the ordinary course of

nature. In short, the direct observations made upon the theory of

"primitive generation" are as yet wanting in necessary exactness; those

observers who profess to have witnessed the sudden origin of the

minutest of the infusoria from elementary substances have in all

probability overlooked the organic structure of these elementary bodies.

The wonderful changes of form undergone by many infusoria have their

limits, and the laws governing them have still to be defined. With the

poet we may say:

"Grammatici certant et adhuc sub judice lis est."

Many of the Infusoria are subject to metamorphoses, and it has already

been ascertained that certain species which have been considered as

distinct are only transition forms of the same species depending on age.

We know that it is common for insects to enclose themselves in

protecting envelopes, and to remain for whole months shut up in this

their retreat, to all appearance dead. Similar facts have been observed

in the Infusoria. We have even seen some of these beings surrounding

strange bodies as if in a mass of jelly, forming a sort of living

envelope around them.

The average duration of life with them is only a few hours; but certain

species present, in relation to the duration of life, phenomena which

are only imperfectly known, but which never fail to excite the surprise

and admiration of the naturalist. By drying certain infusoria with care,

it is possible to suspend and indefinitely prolong its life. Thus dried,

and covered with a powder, which shelters it from every breath of wind,

it may be carried to any given distance, through any indefinite period

of time--abandoned on some ledge of rock, on a housetop, in the cleft

of a wall, or under the capital of a column; but let a drop of water

approach it, and the dormant being awakes immediately--the microscopic

Lazarus springs again into existence: feeds and multiplies as before:

and its life, suspended possibly for years, resumes its interrupted

course!

Into what a world of reflection does not a revelation of this mysterious

property of a living creature plunge us!

The physiologist Müller has noted another peculiarity in infusorial

life. These animalcules can lose a part of their bodies without being

destroyed; the dead part disappears, and the individual, diminished by

one-half, or reduced to a fourth of its former size, continues to live

as if nothing had happened. Müller has observed a kalpode (_Kolpoda

meleagris_) thus melt before his eyes until scarcely a sixteenth part of

its body remained. After its loss, this sixteenth part of an animal

continued to swim about without troubling itself as to its diminished

proportions. "The infusoria," says Frédol, in "La Monde de la Mer,"

"present yet another kind of decomposition. If we approach the drop of

water in which it swims with the barb of a feather dipped in ammonia,

the animalcule is arrested in its movement, but its cils continue to

move rapidly. All at once, upon some point of its circumference, a notch

is formed, which increases bit by bit until the whole animal is

dissolved. If a drop of pure water is added, the decomposition is

suddenly stopped, and what remains of the animalcule recommences its

swimming movements." (Dujardin.)

We may divide the Infusoria into two orders--the _Ciliate Infusoria_,

namely, those provided with vibratile cilia, and the _Flagelliferous

Infusoria_, those, namely, which have arms or branches. The greater part

of Infusoria belong to the first order, which comprehends many families;

our space limits us to the mention here of a few typical forms only in

each group, selecting those which appear the most interesting, from

their size, structure, rarity, or abundance.

FLAGELLIFEROUS INFUSORIA.

The family of _Vibrionidæ_, so named from their darting or quivering

motion, includes the eel-like microscopic animalcules which occur in

stale paste, vinegar, &c., with some others, which are parasitic on

living vegetables, such as _Vibrio tritici_, which infest the grains of

wheat, producing the destructive disease called corn-cockle or purples.

They are filiform animals, extremely slender, without appreciable

organization, internal stomach, or apparent organs of locomotion. They

are the first animalcules which show themselves in any infusion of

organic matter. By using microscopes of the highest magnifying power,

traces of very thin, short lines can be perceived, either straight or

sinuous, the thickest of them not exceeding the thousandth part of the

fraction of an inch. They are contractile, and propagated by spontaneous

division, or _fission_. Among them some resemble right lines, more or

less distinctly articulated, and endowed with a very slow movement;

these are _Bacteridæ_. Others are flexuous and undulating, and more or

less lively; these are true _Vibrions_. Others have the body fashioned

in the form of a corkscrew, turning unceasingly upon themselves with

great rapidity; these are the _Spirillidæ_, having an oblong fusiform or

filiform body, which undulates or turns spirally upon itself.

[Illustration: Fig. 30. Bacterium, termo (Müller), magnified 600 times.

The same, magnified 1600 times.]

The _Bacterium termo_ (Fig. 30) is the smallest of the Infusoria. It is

found, at the end of a short time, in all vegetable or animal infusions

exposed to the air. It shows itself in infinite numbers, forming swarms

of animalcules, which disappear as other species multiply in the liquid,

to which animals it serves for nourishment. When the infusion becomes

too foetid for these new species to live in it, in consequence of

fermentation or putrefaction, the _Bacterium termo_ reappears. This

species was one of the first observed; Leuwenhoek found it in the white

matter in the teeth and gums, which is called teeth tartar. It is also

found in the fluids of various animals which have been affected by

disease.

[Illustration: Fig. 31. Vibrion baguette (Müller), magnified 300 times.]

The _Wand-like Vibrion_ (Fig. 31) has the body transparent, filiform,

with long articulations, often appearing as if broken at each

connection. It moves very slowly in the water. Leuwenhoek observed this

second species joined to the first in the teeth tartar, and also in a

great number of organic infusions. "There is no microscopic object,"

says Dujardin, "which excites the admiration of the observer more

vividly than the twisting spirillum" (Fig. 32). He is struck with

surprise when he first contemplates this little creature, which, under

the greatest magnifying power, only presents the appearance of a thin

black line, fashioned like a corkscrew, which every instant turns upon

itself with marvellous velocity, such as the eye can scarcely follow, or

the mind divine the cause which produces this startling phenomenon.

[Illustration: Fig. 32. Spirillum tournoyant (Ehr.), magnified 300

times.]

The _Monads_ are other infusorial animalcules which make an early

appearance in vegetable infusions. They constitute a family that are

destitute of any covering. The substance of their bodies can swallow

itself, or draw itself out more or less; many of the whip-like filaments

serve as organs of locomotion. They are sometimes provided with lateral

appendages disposed as a kind of tail. Their organization is extremely

simple; their whip-like filaments are so fine as to be scarcely

perceptible, their length being sometimes double and even quadruple the

length of the animal itself.

The _Lentille Monad_ (Fig. 33) is a species which is frequently met with

in vegetable and animal infusions. The older microscopists had it

indicated under the form of a globule, moving in a slow and vacillating

manner. The globule is formed of a homogeneous transparent substance,

swollen into tubercles on its surface, and throws out obliquely a

whip-like filament, three, four, or even five times the length of the

body of the Monad.

The _Cercomonad_ of Davaine was discovered by this gentleman in the

still warm ejections of cholera patients. Its body is pyriform, having,

in front, a vibratile filament, very long, very flexible, and easily

agitated. Behind the body there is a thicker straight filament attaching

itself sometimes to neighbouring corpuscles, round which, in this case,

the _Cercomonad_ oscillates like the ball of a pendulum round its stem.

[Illustration: Fig. 33. Monade lentille (Dujardin), magnified 1000

times.]

The _Volvocineæ_ are inhabitants of fresh limpid water full of confervæ

and other aquatic plants. The _Volvocineæ_ are, according to Dujardin,

animalcules of a green or yellowish brown colour, regularly disseminated

in the thickness and near the surface of a gelatinous and transparent

globe, which would become hollow and be filled with water in its perfect

state. In this state, from five to eight smaller globules, with the same

organization, appear destined to undergo the same changes when they are

released by the rupture of the globule. These animalcules are each

furnished with one or two flagelliform filaments, which, by their

agitation, determine the movement by rotation of the mass.

A very remarkable phenomenon is recorded in the Transactions of the

Microscopic Society, namely, the conversion of the contents of an

ordinary vegetable cell into a free moving mass of Protoplasm, bearing a

strong resemblance to the animal _Amoebæ_ (Fig. 20). This, it is

affirmed by Dr. Hicks, takes place in Volvox, under circumstances which

suggest a vegetable transformation. But Dr. Carpenter does not consider

that this involves any real confusion in the boundaries of Animal and

Vegetable Life.

[Illustration: Figs. 34 and 35. Volvox globator (Müller), magnified 700

times.]

The Revolving Volvox, _V. globator_ (Figs. 34 and 35), is found in great

abundance, during summer, in tanks and ponds of stagnant water. It

consists of green or brownish-yellow globules about the eighth part of

an inch, formed of animalcules scattered round a gelatinous and

diaphanous spherical membrane, each furnished with a flagelliform

filament and with a reddish interior point, which Ehrenberg took for an

eye. Leuwenhoek first observed this Volvox in marshy waters. This

eminent naturalist has left a very interesting account of his

observations on these microscopic inhabitants of the waters, displaying

an amount of patience and address which cannot be too much admired; his

observations were made with a simple lens, which he constructed himself.

In one hand he held his instrument, which was very coarse if we compare

it to the more perfect and infinitely more powerful instruments now in

use; whilst, in the other hand, he carried to his eye the glass tube

full of water which contained the object under observation. "The

microscopes of Leuwenhoek," says Dujardin, "were the very smallest

bi-convex lenses, mounted in a silver frame. He made a collection of

twenty-six, which he bequeathed to the Royal Society of London. These

instruments, subject to all the inconveniences of a maximum of

spherical aberration and a total want of stability, were only fit for

use in the hands of Leuwenhoek himself, who had acquired, in his labour

of twenty years, habits of observation which compensated, in great part,

for the want of perfection in his instruments."

The _Eugleniæ_ are infusoria usually coloured green or red. Their form

is very variable. They are oblong or fusiform in shape, swelling at the

middle during action, and contracted or bowl-shaped in repose, or after

death. They are furnished with the usual whip-shaped filament, which

issues from an opening in front, and from one or many reddish points

irregularly placed anteriorly.

_Euglenia viridis_ (Fig. 36) is the most common species, and, perhaps,

the most widely diffused of all the Infusoria. It is this animalcule

which habitually covers stagnant pools with its floating surface of

green, and which forms, on the surface of marshy waters, the shining

pellicle so strongly coloured, which, collected upon paper, so long

preserves its brilliant tint.

[Illustration: Fig. 86. Euglenia viridis (Ehr.), magnified 350 times.]

The _Euglenia sanguinea_, at first green, becomes subsequently of a

blood colour. It has often been met with by microscopists. Ehrenberg,

who first described it, attributes to its great abundance the red colour

of some stagnant waters. Its presence explains the pretended miracle of

water changing into blood, which was frequently invoked by the Egyptian

priests.

CILIATE INFUSORIA.

Let us now take a glance at some of the more remarkable species of

Ciliate Infusoria. The bodies of these creatures are all more or less

translucent. They have not substance enough, in fact, to reach a state

of opacity. Their bodies are more or less globular or ovoid, sometimes

fashioned like a shuttle, or curved while growing, sometimes swollen in

the middle like an ampulla, or bell-shaped, and flattened into a discoid

shape; some slightly resemble a tadpole, a thimble, a shoe, a rose-bud,

a flower, even a seed.

[Illustration: Fig. 37. Cothurnia pyxidiformis (Udckem).]

The Paramecians have a soft flexible body, usually of oblong form, and

more or less depressed. They are provided with a loose reticulated

covering, through which issue numerous vibratile cilia, arranged in a

regular series. They were known to the older naturalists; and it is in

this group that organization is carried to the highest perfection it

attains among the Infusoria. The Paramecium possess, besides their

reticulated and contractile tegument, cilia disposed in such a manner as

to serve at once for locomotion, for prehension, that is, for seizing

its food, and as a means of respiration. They are furnished with a

mouth, at the bottom of which the whorl excited by the cilia determines,

according to Dujardin, the hollowing out of a cavity, formed after the

manner of a cul-de-sac, and also the formation of _vacuoles_ with

permanent partitions, in which are enclosed the substances which the

animalcules have swallowed along with the water.

[Illustration: Fig. 38. Paramecium bursaria (Pritchard).]

The Paramecium are propagated by spontaneous division, as already

described. They abound, as we have said, in stagnant water, or in pure

water which is occupied by aquatic plants, sometimes in such prodigious

quantities that they become troublesome. They occur also in flower vases

where the water is not frequently renewed.

The species of this genus have an oblong compressed body, with an

oblique longitudinal fold, directed towards the mouth, which is

lateral. They are sufficiently large to be observed by the common lens,

or eye-glass. _Paramecium aurelia_ appears chiefly in vegetable

infusions. It is common in ditches and moats with aquatic plants.

Humboldt's assertion is fully verified in the case of the Infusoria

under consideration, which is often found with its parasites. These are

small creatures, cylindrical in form, and provided with suckers.

Swimming vigorously in the water, they devote themselves to chasing the

Paramecium. When they have overtaken the fugitive, they throw themselves

upon it, and establish themselves there. They soon multiply in the

interior of its body, and their starving progeny suck and devour the

unfortunate animalcule, which serves them at once for dwelling-house and

larder.

[Illustration: Fig. 39. Condylostoma patens (Duj.), magnified 350

times.]

Another of the parasites which prey upon the Paramecium, in place of

pursuing it, remains perfectly quiet until one of these approach, when

it throws itself upon its victim, and is carried along with it. It

buries itself in the body of the Paramecium, and, in a short time,

multiplies to such a degree, that sometimes fifty of them are found on a

single individual. Poor victim!

The _Nassula_ have the body entirely covered with cilia; they are ovoid

or oblong in form, contractile, the mouth placed laterally and dentate,

or surrounded with a band of horny bristles, the band dilating and

contracting according to the size of the prey which it would swallow. It

either advances to seize the prey, which the movement of vibratile cilia

have failed to draw within the vortex of its mouth, or, as in the case

of the Paramecium, it is sometimes obliged to seek for its prey. These

curious infusoria live in stagnant waters, feeding on the débris of

aquatic plants, from which they draw their chief nourishment as well as

their colour.

The _Bursarians_ are animals with an oval or oblong contractile body,

provided also with vibratile cilia, especially on the surface, having

also a large mouth, surrounded with cilia, forming a sort of microscopic

moustache, spirally arranged.

Among the species belonging to this group may be noted the _Condylostoma

patens_ (Fig. 39), remarkable for its size and voracity. It sometimes

attains the twelfth of an inch, and abounds on every shore from the

Mediterranean to the Baltic. Another Bursarian, a species of

_Plagiostoma_, lives between the intestines and the external muscular

bed of the earth-worm, _Lumbricus terrestris_. To the group of

_Urceolarians_ belong the _Stentors_, which are in number the most

numerous of the Infusoria; they are, for the most part, visible to the

naked eye.

[Illustration: Fig. 40. Stentor Muelleri (Enr.), magnified 75 times.]

The _Stentors_ are inhabitants of fresh, tranquil water, not subject to

agitation, and covered with water plants. They are nearly all coloured

green, blackish, or blue; their bodies covered with cilia. They are

eminently contractile, and very variable in form. They can attach

themselves temporarily, by means of the cils at their posterior

extremities, when they assume a trumpet-like form, the bell of which is

closed by a convex membrane, the edge being furnished with a row of very

strong obliquely-placed cilia, ranged in a spiral, meeting at the mouth,

which is placed near this edge. When they swim freely, they alternately

resemble a club, a spindle, or a sphere. The _Stentor Muelleri_ is seen

in ponds in the neighbourhood of Paris and elsewhere; it has been found

even in the basins of the Jardins des Plantes (Fig. 40).

The animals which constitute this genus are fixed in the first part of

their existence, but free in the second. So long as they are fixed, they

resemble, in their expanding state, a bell or funnel, with the edges

reversed and ciliate. When they become free, they lose their crown of

cilia, take a cylindrical form, more or less ovoid and elongated, and

move themselves by means of a new organ. "There is no animal," says

Dujardin, "which excites our admiration in a higher degree than the

Vorticellate Infusoria, by their crown of cilia, and by the vortex which

it produces; by their ever-varying forms; above all, by their _pedicle_,

which is susceptible of rapid spiral contraction, by drawing the body

backward and again extending it. This _pedicle_ is a flat membranous

band, thicker upon one of its edges than the other, and containing on

the thicker side a continuous channel, occupied, at least in part, by a

fleshy substance, analogous to that of the interior of the body. During

contraction, this thick edge is shortened more than the thin side, and

hence results the precise form of the spiral of the corkscrew."

We cannot conclude our brief history of these curiously-organized beings

without recording the doubt which still exists in the minds of our most

eminent naturalists, whether some of those we have named are animal or

vegetable in their origin. The _Desmideæ_, long classed among animals,

are now generally recognized as plants. The group of _Diatomaceæ_ are

still considered doubtful, and the Monads and _Volocina_ are still

subjects of discussion, the evidence inclining in favour of those who

argue for their vegetable nature. Messrs. Busk, Williamson, and Cohn,

have published in the "Microscopical Transactions" minute details of the

evolutions of these curiously-organized globules, which seem to prove

their vegetable nature. On the other hand, it is difficult to imagine so

accurate an observer as Agassiz writing so positively as he does on a

doubtful subject. Remarking on a former paper, in which he had shown

that the embryo hatched from the egg of a Planaria was a true

polygastric animalcule of the genus Paramecium, he adds, that in former

writers a link was wanting, viz., tracing the young hatched from the egg

of _Distoma_. "This deficiency," he says, "I can now fill. It is another

_Infusorium_, a genuine _Opalina_. With such facts before us there is no

longer any doubt left respecting the character of all these Polygastria;

they are the earliest larvæ condition of worms." Amid these friendly

disputes we congratulate ourselves that we have to do with the oceanic

creations, both animal and vegetable.