CHAPTER IX.

ECHINODERMATA.

"Ultra magis pisces et Echinos æquora celent."--_Hor. Ep._

In their "Natural History of the Echinodermata," Messrs. Hupé and

Dujardin divide this vast natural group into five orders or families,

namely: 1, _Asteroïdæ_, which includes the true star-fishes; 2,

_Crinoïdæ_, stone lilies, calcareous, stem composed of movable pieces;

3, _Ophiuræ_, having the disk much depressed, the rays simple, and

furnished with short stems; 4, _Echinidæ_, comprehending the animals

known as sea-eggs, or sea-urchins, distinguished by their rounded form

and absence of arms; 5, _Holothuroïdæ_, with soft lengthened cylindrical

body, covered with scattered suckers.

The Echinodermata, from the Greek words ἐχῖνοϛ, rough, and

δέρμα, skin; indicating an animal bristling with spines like

the hedgehog's. They are animals sometimes free, sometimes attached by

a stem, flexible or otherwise, and radiating, that is, presenting an

appearance more or less regular in all its parts, after the manner of

a circle or star, its form being globular, egg-shaped, cylindrical, or

like a pentagonal plate; or, lastly, like a star, with more or less

elongated branches, which secrete either in all their tissues or only

in the integument very numerous symmetrical calcareous plates of solid

matter, sometimes forming an internal skeleton or regular shell covered

with a more or less consistent skin, often pierced with holes, from

which the feet or tentacula issue; they are frequently furnished with

appendices of various kinds, such as prickles, scales, &c.

The organization of the Echinodermata is the most perfect of all the

zoophytes, serving as a transition between them and animals of more

complicated frame. They have a digestive and vascular system, and a

muscular system is almost always present; in short, they have internal

or external respiratory organs, and a rudimentary nervous system has

been detected in many of the species. The nutritive system is very

simple, presenting in most of the family a single orifice in the centre

of the lower surface of the body, destitute of teeth, performing the

functions both of mouth and anus. De Blainville says that "the liver is

apparent and rather considerable in the star-fishes, forming bunches

occupying the whole circumference of the stomach, and extending to the

cavities of the appendages where these exist." The mouth and gullet is

admirably adapted for securing the testaceous mollusks and other

substances on which they feed.

Reproduction in the Echinodermata appears to be monoecious. Ovaries are,

as far as is known, the only organs of generation. They vary in number

in different species. The sexes are usually separate: the young are

produced by eggs, the embryo of which undergo important metamorphoses.

Immediately after birth, the young asteriæ have a depressed and rounded

body, with four club-shaped appendages or arms at their anterior

extremity. When they are a little more developed, papillæ may be

observed on the upper surface, in fine radiating rows: after twelve days

the fine rays begin to increase, and after eight days more two rows of

feet, or tentacula, are developed under each ray, which assist in the

locomotion of the animal by alternate elongation and contraction,

performing also the office of suckers. Like most other zoophytes, they

have the power of reproducing parts of their bodies which may have been

accidentally destroyed.

ASTERIAS, OR STAR-FISHES.

As to the animal which commonly and sometimes scientifically bears the

name of Star-fish, in walking on the sea-shore at low tide, your eyes

have often seen this strange creature half buried in the sand. It is so

regular and geometrical in its form that it has more the appearance of

being the production of man's hand than of a creation which breathes and

moves. The Divine Geometrician who created it never realised a creature

more regularly finished in shape, or more perfectly harmonious in

symmetry.

The _star-fish_ has five perfectly equal arms. They resemble a cross of

honour, which has five branches. The _star of the brave_, the _star of

honour_--these somewhat trivial words recall, nevertheless, the

resemblance which exists between the two objects; doubtless, man has

here taken Nature for his copy. It must, however, be remarked that,

though five is the general number of lines in the star-fish, this number

is not constant; it varies with different genera, species, and even with

individuals. The connection of the arms with the disk presents equally

remarkable differences. In the genus _Culcita_, the disk is so much

developed that it constitutes, so to speak, the entire animal, whilst

the arms form only a slight protuberance upon its circumference. In the

genera _Luidia_, on the contrary, the disk is reduced to minimum, whilst

the arms are of great length and very slender.

[Illustration: Fig. 105. Asterias rubens (Lamarck).]

The colours of the _star-fish_ vary greatly; they vary from a

yellowish-grey, a yellow-orange, a garnet-red, to a dark violet, as

their name indicates.

_Star-fishes_ are exclusively and essentially beings of the sea; they

are never seen in fresh water; they dwell amongst the submarine herbage,

seeking for sandy coasts; they generally are found at moderate depths,

but there are some species which are found at the great depth of a

hundred and fifty fathoms.

Asterias are met with in almost every sea and under all latitudes, but

they are most numerous and their forms are more richly varied in the

seas of tropical regions. There are about a hundred and forty species

described.

[Illustration: Fig. 106. Asterias aurantiaca (Lamarck).]

The body of the Asteria is supported by a calcareous envelope composed

of juxta-posed pieces at once various and numerous. The number of these

pieces is estimated at more than eleven thousand in the Red Sea

Star-fish (_Asterias rubens_, Fig. 105), a species very common in

Europe. The body of the _Asterias rubens_ is likewise furnished with

spines, granules, and tubercules, the shape, number, and disposition of

which serve to characterise the genera and the species.

Another species, _Asterias aurantiaca_, will give an exact idea of the

general type of animals of this order. This zoophyte, which is

represented in Fig. 106, is common in the northern seas; it has five

rather long arms, furnished with spines which are of an orange

colour--hence its name. When we see one of these animals stranded upon

the shore, it appears to be entirely destitute of all power of

progression. But the _star-fish_ is not always immovable; it is provided

with an apparatus for locomotion, which appears to serve at the same

time the purposes of respiration; for nature is not sparing in her gifts

to the least organized beings; she bestows upon them feet, with

respiratory organs, or lungs, which have the power of locomotion.

The muscular system, as already stated, is almost always present in the

Echinodermata, but the organs of locomotion are very various, the

principal being the membranous tubes usually termed feet, or ambulacra,

which issue from the ambulacral apertures; but besides these, the rays

themselves are movable, and in animals which are free to move from place

to place these are used for the purpose. Thus in the common star-fish

the rays may be bent towards the upper or lower surface of the disk, so

as to facilitate its advance either in water over small spaces or up the

vertical face of rocks. These ambulacra are very numerous, disposed in

rows along the under surface of the rays; thus in _A. aurantiaca_ there

are two simple rows of feet attached to each ray, and the vesicular part

is deeply cleft into two lobes; while in _A. rubens_ (Fig. 105) there

are two double rows on each ray, and each foot has an undivided vesicle.

Each of these ambulacra consists of two parts, an internal and generally

vesicular portion placed within the body, and a tubular portion outside,

projecting from the surface through an aperture in the skin or shell,

the tube being closed at the extremity, and terminating in a sucker,

usually in the form of a disk slightly depressed in the centre. The feet

are thus muscular fleshy cylinders, hollow in the centre, and very

extensible; by means of them the animal draws itself forward. The foot

is extended by the contraction of its internal vesicle, which forces the

fluid into the hollow tube, or, where the vesicle is wanting, by

projecting the fluid into the tube by a communicating vessel. The

tubular part is thus distended and elongated, and again retracts itself

by means of its muscular fibres, by which action the fluid is forced

back into the interior. In progression the animal extends a few of its

feet, attaches its suckers to the rocks or stones, then, by shortening

its feet, it draws its body forward. The progression of the Asterias is

thus very slow, and so regular that only the closest observation enables

the spectator to discover the movement which produces it. Like the

movements of the hands of a watch, the eye cannot quite follow it. When

an obstacle presents itself--if, for example, a stone comes in its

way--it raises one of the rays in order to obtain a point of support,

then a second ray, and, if necessary, a third,--and thus the animal

creeps over the stone with as much ease as if it walked over the smooth

sands. In the same way the animal creeps up perpendicular rocks, which

is accomplished by means of these ambulacra and suckers. Frédol says:

"If an Asteria is turned upon its back it will at first remain

immovable, with its feet shut up. Soon, however, out come the feet, like

so many little feelers; it moves them backward and forward, as if

feeling for the ground; it soon inclines them towards the bottom of the

vase, and fixes them one after the other. When it has a sufficient

number attached the animal turns itself round. It is not impossible,

whilst walking on the sea-shore, to have the pleasure of seeing one of

these star-fishes walking upon the sand. A day rarely passes without one

of them being thrown upon the strand by the tide, and then abandoned by

the retreating waters. Generally they are left dead; this is not always

the case, however; they are sometimes only benumbed. Place them in a

vase full of sea-water, or simply in a pool on the shore, and you will

sometimes see them recover from this death-like condition, and execute

the curious movements of progression which we have described." The

motions of an Asterias thus saved form a very curious spectacle.

The mouth of this animal is situated on the lower surface of the disk.

At this point the constitutive pieces of the carapace leave a circular

space, covered by a fibrous resistant membrane, pierced at the centre by

a rounded opening. This opening is sometimes armed with hard papillæ,

which play the part of teeth. The mouth almost directly abuts on the

stomach, which is merely a globular sac, filling nearly all the central

portion of the visceral cavity.

"Thus," says Mr. Milne Edwards, "in _Asteracanthion glacialis_ the

stomach is globulous, but imperfectly divided into two parts by a fold

of its internal membrane; the first chamber, thus limited, appears to be

more especially devoted to the transformation of the elementary matter

into a liquid paste, which passes, in small portions, into the upper

chamber. This is continued upward through a small intestine, and

communicates laterally with five cylindrical prolongations, which each

divide themselves again into two much elongated tubes, furnished with a

double series of hollow branches, each terminating in a cul-de-sac."

These organs advance into the interior of the rays or arms of the

Asterias.

Imagine, then, an animal bearing digestive tubes in its arms--the same

organ serving for digestion and progression. What lessons in economy

does not the study of nature teach us! The products of digestion find an

absorbent surface of great extent in the rays of the Asterias. They

ought necessarily to pass rapidly from it into the circumjacent

nourishing fluid.

The star-fishes are very voracious; they even attack mollusks which are

covered with shells. M. Pouchett mentions having taken eighteen

specimens of _Venus_ intact, each being six lines in length, from the

stomach of one large Asterias which he dissected upon the shores of the

Mediterranean. It is now even said that the star-fishes eat many

oysters.

Ancient naturalists were not ignorant that the star-fish was capable of

eating oysters; but they believed that they waited for the moment when

the bivalve would open its valves to introduce one of their rays into

the opening. They imagined that having thus put one foot into the

other's domicile, they soon put four, and finished by reaching and

devouring the savoury inhabitant of the shell. Modern observations have

modified the ideas of former naturalists upon this point. In order to

obtain possession of and swallow an oyster, it appears that the

star-fish begins its approaches by bringing its mouth to the closed

edges of the oyster-shell; this done, with the assistance of a

particular liquid which its mouth secretes, it injects a few drops of an

acrid or venomous liquid into the interior of the oyster-shell, which

forces it to open its valves. An entrance once obtained, it is not long

before it is invaded and ravaged. Professor Rymer Jones gives another

explanation of the transaction. According to this naturalist the oyster

is seized between the rays of his ravisher, and held under his mouth by

the aid of his suckers; the Asteria then inverts its stomach, according

to the professor, and envelopes the entire oyster in its inmost

recesses, while, doubtless, distilling a poisonous liquid. The victim is

thus forced to open its shell, and becomes the prey of the enemy which

envelopes it.

Whatever may be the modes of procedure employed by the star-fish, it is

now clearly ascertained, however incredible the fact may at first

appear, that it swallows oysters in the same manner as is practised at

the oyster-shop.

This little being, formed of five arms and without any other apparent

member, accomplishes a work which man is quite unable to execute--it

opens an oyster without an oyster-knife.

If reasoning man had no other means of nourishment than oysters, and was

without a knife to open them, it is very certain that with all his

genius he would be puzzled how to get at the inaccessible and savoury

bivalve so obstinately closed against him. The star-fish devours dead

flesh of all kinds; their sole occupation is to feed themselves, and

they keep up an incessant and active chase after all sorts of corrupt

animal matter. The Asterias thus perform in the bosom of the sea the

same part that certain birds and insects play on shore; they are its

scavengers, and feed their bodies upon the carcases of animals which, if

abandoned to the action of the elements, would become a cause of

infection.

In the same manner that certain animals render the air healthy, the

Asterias help, on a considerable scale, to keep the sea which shelters

them in a pure and healthy state. Zoologists are not agreed upon the

manner in which respiration operates on the star-fishes. Nevertheless

they think that the principal part in this phenomenon devolves upon the

subcutaneous branchiæ which in each ray constitute two double series of

bladders. The function of circulation is equally unknown. The vascular

apparatus is sufficiently developed in this zoophyte, and appears to

have for its centre an elongated canal with muscular walls, which may

with justice be honoured with the name of heart. A little ring

surrounding the oesophagus, and from which issue certain delicate white

chords, which are prolonged into the furrows of the arms, presents us

with all that can be designated a nervous system in the star-fishes.

Among organs of sense we may mention, as the apparatus of touch, the

_tentacular ambulacra_, as well as those which are disseminated upon the

dorsal surface of the disk. The eyes are considered to be certain

bright red points which are situated at the extremity of the arms and on

the under surface--a most singular position for the organs of sight. The

eyes must, besides, be very imperfect, for they possess no crystalline

lens. Ehrenberg insists upon the existence of eyes in some species,

attributing the function to those red spots, however; while Rymer Jones

attributes the indications in which this originates to an extremely

delicate sense of touch in the star-fishes. Professor Edward Forbes,

while he admits the existence of ganglions in the nervous system to be

extremely doubtful, seems, by the frequent use of the terms eye and

eyelids, to admit that the specks in question are visual organs; the

weight of authority inclines therefore to Ehrenberg's view, that if not

eyes in the strict sense of the term, they serve the purposes of vision,

modified and adapted to the wants of the animal.

The star-fishes have distinct sexes, with individual differences; their

eggs, which are round and reddish, undergo curious phases of

development. They produce little worm-like creatures, covered with

vibratile hairs, like the infusoria, which swim about with great

vivacity; these little creatures are subject to considerable changes. In

the year 1835 M. Sars described, under the name of _Bipinnaria

asterigera_, an enigmatical animal resembling a polyp from the arms at

one extremity of the body, while the other terminated in a tail,

furnished with two fins; but it was chiefly remarkable as having an

Asterias attached to the extremity which carried the arm. He expressed

an opinion, which was soon placed beyond any doubt, that this

_bipinnaria_ was an Asterias in its course of development. The egg

becomes a sort of infusoria, the infusoria becomes a _bipinnaria_, and

this produces the Asterias. In short, the Bipinnaria does not become an

Asterias by any metamorphoses analogous to that so well known amongst

insects--the butterfly, for example--but becomes, so to speak, the

foster-mother or nurse to the Bipinnaria. The larva is large, and it is

at the cost of a very small internal rudiment of this larva that the

Asterias is developed: the Asterias robs the larva of its stomach and

intestines, and turns it into a visceral apparatus for its own use. But

the Asterias makes itself a mouth of any of the pieces most remote from

the primitive mouth of the larva. Thus the Bipinnaria divides itself; it

gives its stomach and intestines, and keeps its oesophagus and mouth,

and it can live several days after the Asterias is detached from it.

Can any one imagine the existence of a being with only a mouth and

oesophagus, which has neither stomach nor intestines, because another

animal has possessed itself of them for its own use? The study of the

lower animals abounds in surprises of this kind. It is a chain of

unforeseen facts; of natural impossibilities; of realized points

necessarily reversing all notions obtained in the study of beings which

have a higher place in the animal scale. The history of the star-fishes

would be incomplete were we to omit mentioning the most remarkable

traits of their organisation with which naturalists are acquainted. The

animals exhibit in the highest degree the vital phenomena of

dismemberment and restoration, that is to say, of the faculty of

reconstructing organs which they have lost. These arms, the structure of

which is so complicated, and which protect such important organs, may be

destroyed by accident. The animal troubles itself little at this

mutilation: if he loses an arm it disquiets him but little; another is

immediately procured. We often see in our collections of Asterias

specimens wanting in symmetry because they have been taken before the

new members which are in process of development have attained their

definite length. Professor Rymer Jones mentions an instance of

redintegration very complete and most curious. This naturalist had an

isolated ray of Asterias which he had picked up; at the end of five days

he observed that four little rays and a mouth had been produced; at the

end of a month the old ray was completely destroyed, and this apparently

useless fragment had been replaced by a new being, quite perfect, with

four little symmetrical branches. This faculty of reproducing organs,

which we have noted in describing the fresh water polyps, the sea

anemone, &c., exists also in many other zoophytes, but in none more

strikingly than in the Asterias. But a still more startling fact remains

to be mentioned: one more strange and more mysterious, for it does not

belong to the physical or organic order, but appears to belong to the

moral world. The star-fishes commit suicide! Certain of these animals

appear to escape from dangers which menace them by self-destruction.

This power of putting an end to existence we only find on the highest

and lowest steps of the animal scale. Man and the star-fishes have a

common moral platform, and it is that of self-destruction! This power of

dismemberment, however, seems to be confined to the _Ophiocoma_ and

_Luidia_--at least, it is only carried out to its full extent in these

generæ.

Mysteries of Nature, who can sound your depths? Secrets of the moral

world, what being but God has the privilege of comprehending you? A

large species of Star-fish (_Luidia fragillissima_), which inhabits the

English seas, has this instinct of suicide to a great extent. The

following account by Professor Edward Forbes of an attempt to capture a

Luidia gives a good illustration of its powers. "The first time that I

took one of these creatures," the professor says, "I succeeded in

placing it entire in my boat. Not having seen one before, and being

ignorant of its suicidal powers, I spread it out on a rowing bench, the

better to admire its form and colours. On attempting to remove it for

preservation, to my horror and disappointment I found only an assemblage

of detached members. My conservative endeavours were all neutralised by

its destructive exertions; and the animal is now badly represented in my

cabinet by a diskless arm and an armless disk. Next time I went to

dredge at the same spot I determined not to be cheated out of my

specimen a second time. I carried with me a bucket of fresh water, for

which the star-fishes evince a great antipathy. As I hoped, a Luidia

soon came up in the dredge--a most gorgeous specimen. As the animal does

not generally break up until it is raised to the surface of the sea, I

carefully and anxiously plunged my bucket to a level with the dredge's

mouth, and softly introduced the Luidia into the fresh water. Whether

the cold was too much for it, or the sight of the bucket was too

terrific, I do not know; but in a moment it began to dissolve its

corporation, and I saw its limbs escaping through every mesh of the

dredge. In my despair I seized the largest piece, and brought up the

extremity of an arm with its terminal eye, the spinous eyelid of which

opened and closed with something exceedingly like a wink of derision."

The mind remains confounded before such spectacles, and we can only say,

with Mallebranche, "It is well to comprehend clearly that there are some

things which are absolutely incomprehensible."

This is doubtless the reason that in collections of natural history we

rarely find star-fishes, and especially the Luidia, entire; the moment

the animal is seized by fisherman or amateur, in its terror or despair

it breaks itself up into small fragments. To preserve them whole they

must be killed suddenly, before they have time to be aware of their

danger. For this purpose, the moment they are drawn from the sea they

must be plunged into a vase of cold fresh water; this saltless liquid

is instant death to these creatures, which in this condition perish

suddenly before they have time to mutilate themselves. The star-fish is

a curious ornament in our natural history collections, but in this state

they represent very imperfectly the elegance and particular grace of

this curious type. To understand the star-fishes, they must be seen in

an aquarium, where we can admire the form, figure, movements, and

manners of these marvellous beings.

The Asterias are the planets of the sea. It may be said that heaven,

reflected during the night on the silvery surface of the ocean, let fall

some of those stars into its depths which decorate the resplendent

vault.

CRINOÏDEA.

We quoted the maxim of Linnæus in the earlier pages of this volume, that

Nature makes no leaps. Nature proceeds by means of insensible

transitions, rising by degrees from one organic form to another. Most of

the animals hitherto described are immovably fixed to some solid object;

at least, such is their condition in the adult state. We are about to

describe zoophytes free of all fetters; animals "which walk in their

strength and liberty."

Between zoophytes fixed to the soil, like the corals, gorgons, and

aggregate zoophytes, such as sea-urchins and holothurias, Nature has

placed an intermediate race, namely, the Crinoïdea, a class of zoophytes

which are attached to a rock by a sort of root armed with claws, having

a long flexible stem, which enables them to execute movements in the

circle limited only by the length of this stem, just as the ox or goat

in our paddocks is confined by its tether to the space circumscribed by

the length of its rope.

Let the reader picture to himself a star-fish borne upon the summit of a

flexible stem firmly rooted in the soil, and he has a general idea of

the zoophytes which compose the order of the Crinoïdea. Naturalists of

the seventeenth century bestowed the name of _stone lilies_ on these

curious products. This rather poetical name proves that the conformation

of these creatures had at an early period attracted observation,

presenting the naturalist with the most curious of his lessons. The

encrinites raise, as from the dead, a whole world buried in the abyss of

the past. At the present time only two genera of these zoophytes exist,

whilst in the early ages of the world the ocean must have swarmed with

them. Encrinites abounded in the seas during the transition and

secondary epoch. It was one of the most numerous of the animal tribes

which inhabited the salt waters of the ancient world. In traversing some

parts of France, we tread under our feet myriads of these beings, whose

calcareous remains form vast beds of rock. The encrinites gradually

disappeared from the ancient seas; their species were diminished as the

globe became older or modified in its conditions, so that at the present

time only a few types remain in our seas--such as the _Comatula_ of the

Mediterranean; _Pentacrinus_, the Medusa's-head of the Antilles; and the

European _Pentacrinus_--all of them very rare, and probably destined

soon to disappear, carrying with them the last reminiscence of the

zoological races of the ancient world: and here lies the real interest

which the Crinoïdea presents to the thinking man. The encrinites most

common in the fossil state are _Pentacrinus fasciculosus_, belonging to

the lias; _Apiocrinus rotundus_, which is found in the oolite or

jurassic rocks; and _Encrinus liliformis_, which appertains to the

Triassic period. These three fixed zoophytes seem to have existed in

great numbers during an early age of the world--namely, the Silurian

period. They attained their maximum of development during the Devonian

age, after which they begin to decrease. According to M. D'Orbigny,

there are thirty-nine genera found in the palæozoic rocks, two in the

triassic, seven in the jurassic, five in the cretaceous, and only one in

the tertiary strata. Of all these genera only one, namely,

_Pentacrinus_, is found in the modern epoch to represent the varied

forms of these the first inhabitants of the seas.

The free Crinoïdæ, that is, those not rooted to the soil by a stem, of

which the _Comatula_ may be considered the type, only appeared at a

later period. They are absent in the palæozoic and triassic rocks, but

appear to have attained their maximum of development in the jurassic

period.

The numerous fossilized remains of these curious creations, which abound

in different rocks, attracted the attention of learned men at an early

period. The encrinites were among the earliest objects of scientific

description. As early as the sixteenth century, the celebrated

mineralogist, George Agricola, mentions them under the names of

_Entrochites_, _Trochites_, and _Astroïtes_. At the same time, and

since that epoch, the Crinoïdæ, which we know by the name of

stone-lilies, and which characterises the _Muschelkalk_ rocks, have been

known under the name of Encrinus, from εν, stone, and κρίνον, a

lily.

[Illustration: Fig. 107. Pentacrinus caput Medusæ (Müller).]

During the eighteenth century the works upon the Crinoïdæ were very

numerous, though not very correct. They sometimes reported these organic

remains to be vegetable; sometimes they were beings allied to the

star-fishes; at others they were the vertebral column of fishes. Towards

the year 1761, however, Guettard, one of the most learned naturalists of

his time, understood the real nature of these productions. He had

occasion to examine a recent Encrinus sent from Martinique under the

name of _Sea-Palm_, which was in reality _Pentacrinus caput Medusæ_. The

comparison of the living individual with the fossil fragment described

by his predecessors, and of which he had specimens in his collections,

enabled him to ascertain the real origin of the fossil Encrinoidæ. The

beautiful fragment which still exists in the Museum of Natural History

at Paris was long considered unique, but it is now known that ten others

exist in different museums. Since that date the Crinoïdæ have been

examined and described by observers such as Miller, Forbes, D'Orbigny,

and Pictet, and very elaborately by Major Austin.

[Illustration: Fig. 108. Pentacrinus Europæus (Thompson).]

"The species of fixed Crinoïdæ actually living are _Pentacrinus caput_

_Medusæ_ (Fig. 107), and _Pentacrinus Europæus_ (Fig. 108). These

curious zoophytes resemble a flower borne upon a stem, which terminates

in an organ called the calyx, but which is, properly speaking, the head

of the animal. Arms, more or less branching, spring from this calyx,

their ramifications, so formed, consisting of many pieces articulated to

each other. The calyx is supported by a stem, varying in height, formed

of pieces secreted by the living tissues which surround them. The

articulations of this stem are usually very numerous, cylindrical, and

present a series of rays striated upon their articulated faces. In

_Pentacrinus_ they are prismatic and pentagonal; that is, they present

five projecting angles, and on their articulated face a star with five

branches, or, better still, a rose with five petals. At the base of the

stem of this animal-plant, in many of the Crinoïdæ, we find a sort of

spreading root, which is implanted in the rocks, and is capable of

growing by itself, of nourishing the stem, and of producing new ones.

The root and stem of the fixed encrinites seem to indicate that the

animal can only live with the head erect. Their normal condition is thus

quite different from that of any other of the Echinoderms, almost all of

which keep their mouths invariably directed downwards.

The Medusæ heads are chiefly found on rocky beds, or in the midst of

banks of corals, at great depths. There, firmly fixed by their roots,

their long stems raise themselves vertically; then, with expanded calyx

and long-spreading arms, they wait for the prey which passes within

their reach in order to seize it.

The _Pentacrinus caput Medusæ_ have, as we have said, been fished up

from great depths in the Antilles. Its very small calyx is borne upon a

stem of from eighteen to twenty inches in height, terminating in long

movable arms, the internal surface of which bears its tentacles in a

groove. In the middle of the arms is a mouth, and at the side the

orifice for the expulsion of the digested residuum.

In the Medusæ head and European Pentacrine (_P. Europæus_, Fig. 108),

the presence of a digestive apparatus has been distinctly traced. It is

a sort of irregular sac, with a central mouth on the upper surface, and

another orifice situated at a little distance from the mouth, and

evidently intended as an outlet for the products of digestion. The arms

of these creatures, which are spreading or folded up according to their

wants, are provided with fleshy tentacula, which, serving at once as

organs of absorption and as vibratile cilia, are at the same time organs

of respiration. Such are these curious beings: they occupy a sort of

middle or transition state between animals permanently fixed to some

spot and those capable of motion, representing in our own times the last

remains of extinct generations. Every type of the Crinoïdæ furnished

with arms presents incontestable evidence of their mode of reproduction

or redintegration--that is, of the power of restoring those parts of the

body broken or destroyed by accident; but as we have already drawn the

attention of the reader to this strange faculty of renewing organs

which many of the zoophytes possess, we will not here enlarge further

upon the subject.

* * * * *

The Crinoïdæ are not all like the two species which have been described.

There is an entire family of animals belonging to this class, namely,

the _Comatula_, which are fixed in their early days, but separate

themselves from the rooted stem in their adult age, and, throwing off

the bonds imposed on their youth, live side by side with the asterias,

with whose company they seem much pleased. The encrinites and the

star-fishes thus live in company, and that at prodigious depths, and

under a body of water which no light can reach. Imagine the existence of

animals which pass their lives in such eternal funereal darkness. The

family of Comatula are found in the seas of both hemispheres. Their

bodies are flat--a large calcareous plate formed like a cuirass upon

their backs--presenting, besides, cirri composed of numerous curling

articulations, the last of which terminates in a hook. The ventral

surface presents two orifices: the one in the centre corresponding to a

mouth, the other evidently intended for the discharge of the products of

digestion. This animal is provided with five arms, which diverge

directly from the centre plate or cuirass. The branches of these arms

have _ambulacral grooves_, comprehending a double row of fleshy

tentacles, in the centre of which is the ambulacral groove, properly so

called, clothed with vibratile cilia over their whole surface. These

cilia or hairs guide the current which drives the various substances on

which it feeds, such as the organic corpuscles of sea-weeds, and

microscopic animalcules floating in the sea, towards its mouth. They are

also powerful aids to respiration.

The movements of these curious creatures are very slow, their only

object being to catch the bodies of animals and marine plants, or, by

extending or contracting their arms, to feel their way through the water

to some new locality. Sometimes, also, in order to change their

feeding-ground, the Comatula abandon the submarine forests, herbage, and

sea-wracks, and float through the water, moving their arms with

considerable rapidity in search of a new station.

The Mediterranean Comatula (Fig. 109) is largely diffused on the

European shores of the Mediterranean. Its spreading arms extend to three

or four inches; its colour purple, shaded, and spotted with white upon

the ventral surface.

[Illustration: Fig. 109. Comatula Mediterranea (Lamarck), natural size.]

Were a traveller to tell us that he had seen animals drop their eggs

upon forests of stone; that these eggs, after executing their

progressive evolutions, finally become individuals in all respects like

their parents, which attach themselves to the soil by a root like any

flower of the fields, or to the mother-stem like the branch of a tree,

until in due course they attained the adult state, when the flexible

band which holds them fixed either to the soil or parent-stem breaks,

and the animal, now free, launches itself into the liquid medium, and

goes to live a proper and independent existence;--in listening to a

recital so opposed in appearance to the ordinary laws of Nature, we

should be inclined to tax the narrator of such incredible facts with

error or folly. Nevertheless all these facts are now perfectly

established. The being which presents these marvels has nothing of the

fabulous about it. It is the _Comatula Mediterranea_; it lives at the

bottom of the sea, the surface of which is incessantly tracked by our

vessels.

OPHIURADÆ.

The Ophiuras are thus named from two Greek words (ὅϕις, a serpent, and

οὑρὰ, a tail), from their fancied resemblance to the tail of a

serpent. These zoophytes are met with in almost every sea, but chiefly

in those of temperate regions; they are very common on every shore,

and have been remarked by fishermen from the earliest times on account

of their singular form, the disposition of their arms, which resemble

the tail of a lizard, and by the singularity of their movements. The

general characteristics of this remarkable group of Echinodermata, as

described by Dujardin and Hupé, are as follows. They are radiary marine

animals creeping at the bottom of the sea, or upon marine plants. In

form they present a sort of coriaceous disk, which is either bare or

covered with scales, which contains all the viscera, and five very

flexible simple or branching arms, each sustained by a series of

vertebral internal pieces, naked or covered with granules, scales, or

bristles. Certain fleshy tentacula thrown out laterally are organs of

respiration. The mouth is situated in the middle of the lower surface

of the disk, and opens directly into a stomach in the shape of a sac;

it is circumscribed by five re-entering angles corresponding with the

intervals of the arms, having a series of calcareous pieces, which

perform the function of jaw-bones. This mouth is prolonged by five

longitudinal clefts, garnished with papillæ or calcareous pieces, which

correspond to one of the arms. A series of calcareous pieces in the

shape of vertebræ spring from the extremity of each of these clefts,

which occupy all the interior of the arms, having a furrow in the

middle of the ventral surface for the reception of a nursing vessel;

and laterally between their expansions are certain cavities, from

whence issue certain fleshy retractile tentacula; the visceral cavity

opens by one or two clefts on the ventral surface of each side of the

base of the arms.

The Ophiuradæ move themselves by briskly contracting their arms so as to

produce a succession of undulations analogous to those by which a

serpent creeps along. Some of these zoophytes are rather active; but

others attach themselves by their arms to the branches of certain other

polyps, like the Gorgons, and remain immovable for a considerable time,

waiting their prey somewhat like a spider in the midst of his web.

The family of Ophiuradæ is divided into two great sections: that of the

Ophiura, which comprehends several genera, amongst others that which

gives its name to the family, and that of the Euryalina or Asterophytes.

[Illustration: Fig. 110. Ophiocoma Russei (Lutken), natural size.]

The family of Ophiuradæ constitute a group distinguished by their five

simple, articulated, very mobile, and non-ramified arms, which are

attached to a small disk or shield plate, with flexible thread-like

cirri between the rays. _Ophiura natta_ is very common, and has been

known from very early times in European seas. It is of a greenish

colour, with transverse bands, which become more obscure upon the arms

as the distance from the disk increases. This disk is from six to

seven-eighths of an inch in size, the upper part covered with unequal

plates, in shape like tiles; the arms are four times the length of the

diameter of the disk, very slender and tapering. The zoophyte to which

Lamarck gave the name of _Ophiura fragile_ has now its place among the

Ophisthrix, the specific name, indicating a particularity of structure

in all these small creatures derived from their fragile formation. In

short, these beings have so little consistency that they crumble, as it

were, under the touch, and become reduced to pulp under the slightest

pressure. In Fig. 110 we give the representation of an Ophiura of the

natural size, which Lutken has since called _Ophiocoma Russei_. This

Echinoderm, which lives in the seas of the Antilles, is furnished with

five very flexible rays, which are armed with from three to four rows of

spines, those on the upper part of the body being very hard ones; the

body and arms of this creature are of reddish brown, streaked with a

great number of little white lines.

[Illustration: Fig. 111. Asterophyton verrucosum (Lamarck).]

The principal type of the Euryalina is the curious and complex

_Asterophyton verrucosum_ of Lamarck. They include animals remarkable

for the extremely complicated development of their arms--the very

multiplied ramifications of these, towards the extremities, being

divided into many thousand very slender appendages, the principal use of

which is doubtless locomotion, but at the same time they constitute a

series of living thread-like fillets which seem intended to seize and

close upon the animals which serve as prey to this little flesh-eater.

The _Asterophyton verrucosum_, which is represented in Fig. 111, is

yellowish; its disk about four inches, its arms sixteen to eighteen. It

inhabits the Indian Ocean. Another species, _Euryala arborescens_, is

met with on the coasts of Sicily and other parts of the Mediterranean.

Nothing can be more elegant than these animated disks, which resemble

nothing so much as a delicate piece of lace--a piece of living lace

moving in delicate festoons in the bosom of the ocean.

ECHINIDÆ.

The singular shape of the Echinidæ, or Sea-urchins, and the spiny

prolongations with which their bodies are covered, has in all ages

attracted the attention of naturalists. Aristotle applied to them the

name ἐχῖνοϛ, which signifies urchin. When, however, one sees the

body of one of these animals thrown on the sea shore, it is difficult,

at first, to find a reason for this designation. The body of the

sea-urchin is furnished with a species of spine. It is a sort of shell,

nearly spherical, empty in the interior, its surface presenting reliefs

admirable for their regularity--an egg-shell sculptured by Divine

hands. In order to see the urchin with its spines, it is necessary to

seize it in the water at the bottom of the sea, where it rolls and

moves its little prickly mass; it is then only that the real urchin,

the prickly sea-urchin, is to be seen, bristling with prickles, and

strongly resembling, to compare the physical with the mental, those

amiable mortals whose character is so well depicted in the saying,

"Whom they rub they prick."

In his book on "The Sea," Michelet puts the following conversation into

the mouth of a sea-urchin:

"I am born without ambition," says the modest Echinoderm. "I ask for

none of the brilliant gifts possessed by those gentlemen the molluscs. I

would neither make mother-of-pearl nor pearls; I have no wish for

brilliant colours, a luxury which would point me out; still less do I

desire the grace of your giddy Medusas, the waving charm of whose

flaming locks attracts observation and exposes one to shipwreck. Oh

mother! I wish for one thing only: _to be_--to be without these exterior

and compromising appendages; to be thick-set, strong, and round, for

that is the shape in which I should be the least exposed; in short, to

be a centralized being. I have very little instinct for travel. To roll

sometimes from the surface to the bottom of the sea is enough of travel

for me. Glued firmly to my rock, I could there solve the problem, the

solution of which your future favourite, man, seeks for in vain--that of

safety. To strictly exclude enemies and admit all friends, especially

water, air, and light, would, I know, cost me some labour and constant

effort. Covered with movable spines, enemies will avoid me. Now,

bristling like a bear, they call me an urchin."

[Illustration: Fig. 112. Echinus mamillatus (Lamarck), natural size.]

Let us now look a little more closely at the general structure of the

sea-urchins--in zoological language, Echinidæ.

[Illustration: Fig. 113. Echinus mamillatus. Sea Urchin, without spines,

natural size.]

The body of the sea-urchin is globular in form, slightly egg-shaped, or

of a disk slightly swollen. It consists essentially of an exterior shell

or solid carapace, clothed in a slight membrane furnished with vibratile

cilia. This carapace is formed of an assemblage of contiguous polygonal

plates, adhering together by their edges. Their arrangement is such that

the test or shell may be divided into vertical zones, each springing

from a central point on the summit terminating at a point of the

spheroid diametrically opposite--namely, the circumference of the buccal

orifice. These vertical zones are of two kinds, some larger and others

straighter, each zone consisting of a double row of plates, the first

charged with movable spines, the second pierced with holes disposed in

regular longitudinal series, from which emerge certain fleshy tentacula,

which, as we shall see presently, serve as feet to the animal. When

armed with these bristling spines, the sea-urchins resemble the

hedgehogs; but when the spines are down, they look very much like a

melon or an egg, to which their shape and calcareous nature have

sometimes led to their being compared by the vulgar as well as by the

learned. We shall give a tolerably exact idea of the two different

aspects which the carapace of the urchin presents when the spines are

erect and lowered, by reference to Fig. 112 (_Echinus mamillatus_),

which represents the animal bristling with spines, and Fig. 113, in

which the same species is represented after death, when deprived of

these weapons of defence: and how complicated these defences must be! It

has been calculated that more than ten thousand pieces, each admirably

arranged and united, enter into the composition of the shell of the

sea-urchin, to which no other can be compared. To abbreviate slightly

Gosse's description of that wonderful piece of mechanism, the

sea-urchin: "A globular hollow box has to be made, of some three inches

in diameter, the walls of which shall be scarcely thicker than a wafer,

formed of unyielding limestone, yet fitted to hold the soft tender parts

of an animal which quite fills the cavity at all ages. But in infancy

the animal is not so big as a pea, and it has to attain its adult

dimensions. The box is never to be cast off or renewed; the same box

must hold the infant and veteran urchin. The limestone can only increase

in size by being deposited. Now the vascular tissues are within, and the

particles they deposit must be on the interior walls. To thicken the

walls from within leaves less room in the cavity; but what is wanted is

_more_ room, ever more and more. The growing animal feels its tissues

swelling day by day, by the assimilation of food. Its cry is, 'Give me

space! a larger house, or I die!' How is this problem solved? Ah! there

is no difficulty. The inexhaustible wisdom of the Creator has a

beautiful contrivance for the emergency. The box is not made in one

piece, nor in ten, nor a hundred. Six hundred distinct pieces go to make

up the hollow case; all accurately fitted together, so that the perfect

symmetry of the outline remains unbroken; and yet, thin as their

substance is, they retain their relative positions with unchanging

exactness, and the slight brittle box retains all requisite strength and

firmness, for each of these pieces is enveloped by a layer of living

flesh; a vascular tissue passes up between the joints, where one meets

another, and spreads itself over the whole exterior surface."

This being so, the glands of the investing tissue secrete lime from the

sea water, and deposit it after a determinate and orderly pattern on

every part of the surface. Thus the inner face, the outer face, and each

side and angle of polyhedron, grow together, and the form characteristic

of the individual is maintained with immutable mathematical precision.

The dimensions and shape of these prickles are very variable. In certain

Echinidæ they are three or four times the diameter of the body. In the

urchin, properly so called, they are only three-fourths or four-fifths

that diameter. They sometimes resemble short bristles. These defensive

weapons have tubercles for supports, which are arranged on the surface

of the animal with perfect regularity. At the base they present a small

head separated by compression. This head is hollow on its lower face,

presenting a cavity adapted to a tubercle of the shell. Each of the

prickles, notwithstanding its extreme minuteness, is put in action by a

muscular apparatus.

[Illustration: Fig. 114. Echinus esculentus (Lamarck), natural size.]

In the prickles, or spines and tentacula (ambulacra, _feet suckers_), we

see the external organs of the Echinodermata. The former are instruments

of defence and progression; the latter, strange as it may appear, serve

them to walk with. When it is considered that each of these prickles is

put in motion by several muscles, it is impossible to repress our

wonder and surprise at the prodigious number of organs brought into

action in the sea-urchin. More than twelve hundred prickles have been

counted upon the shell of _Echinus esculentus_, a representation of

which is given in Fig. 114. If we add to this first supply of spines

other smaller and in some sort accessary spines, we shall arrive at a

total of three thousand prickles. Each sea urchin thus bears as many

weapons as ten squadrons of lancers. When it is considered, further,

that in each sucker or ambulacra there exist not less than a hundred

tubes, each having an orifice, you will have a total of four thousand

visible appendages upon the body of an animal of very small dimensions.

If it is considered, finally, that no shell exists more admirably

symmetrical, elegant, or more highly ornamental than the carapace of the

urchin, it will readily be admitted that Nature has been most prodigal

in her gifts to one of the humblest beings in creation--a creature which

passes its existence in crawling in obscurity at the bottom of the sea.

What elegance of form, eternally hidden from the eyes of man, sleeps

under the heavy mass of water; and yet man imagines that everything in

Nature has been created for his use and for his glory.

M. Hupé records a somewhat curious observation in connection with the

spines, which serve as a means of defence to the Echinodermata. He found

a small mollusc, of the genus _Stelifera_, which had sought shelter in

_Leixidaris imperialis_, an urchin, native of Australia; in a word, the

interior of one of these prickles had been hollowed and enlarged so as

to serve as a retreat for this improvised guest.

What unexpected facts does the study of animals present! Nature has

bestowed a protecting armour upon one little being; another still

smaller animal discovers this, and places itself for shelter under the

protection of these levelled bayonets! Numerous anecdotes are told of

them. Thus: a man ignorantly put into his mouth one of these creatures,

with all its prickles, and, being detected, thought himself, in his

pride, compelled to swallow it because he was being looked at;

immediately his mouth was full of blood. The next day he was in such a

state of suffering that he could neither eat nor drink, and for a long

time his life could only be preserved by nourishing injections of soup,

cream, and rice.

Now let us see by what organic mechanism the urchin contrives to

transport itself and walk. The tentacula, or suckers, are hollow

internally, and, as we have said, are provided with small muscles. By

the influx of liquid which they inclose they become inflated throughout

all their prickles, in such a manner that they can attach themselves to

any solid body, at the will of the animal, by means of their terminal

suckers. Frédol, in "Le Monde de les Mers," thus explains the urchin's

mode of progression. "Let us imagine," he says, "one of these creatures

to be at rest; all its spines are immovable, and all its filaments

repose within the shell; some of these involuntarily escape; they extend

themselves and feel the ground all round them: others follow, but the

animal is firmly fixed. If it wishes for change of place, the anterior

filaments contract themselves, whilst the hinder ones loosen their hold,

and the shell is carried forward. The sea-urchin can thus advance with

ease, and even rapidity. During his progression the suckers are only

slightly aided by the spines. It can travel either on the back or

stomach; whatever their posture, they have always a certain number of

prickles, which carry them, and suckers, with which they attach

themselves. In certain circumstances the animal walks by turning upon

itself, like a wheel in motion."

Nothing is more curious than to see a sea-urchin walk upon smooth sand.

But for the colour, it might be mistaken for a chestnut with its

bristling envelopes, the spines serving as feet to put the little round

prickly mass in motion. They have even been observed to form themselves

into a ball, and roll along like a globular fagot of prickles.

[Illustration: Fig. 115. Buccal armature of Echinus lividus.]

One of the most singular organs of the sea-urchin is its mouth. It is

monstrous. Placed underneath the body it occupies the centre of a soft

space invested with a thick resisting membrane: it opens and shuts

incessantly, showing five sharp teeth (Fig. 115) projecting from the

surface, the edges meeting at a point, as represented here, supported

and protected by a very complicated framework, which has received the

name of Aristotle's Lantern (Fig. 116). Fig. 115 represents _Echinus

lividus_ in its normal state; the other shows the masticatory organs,

that is to say, Aristotle's Lantern. To give the reader a more complete

idea of the buccal organ in the sea-urchin, let him glance at one from

the southern seas, _Clypeaster rosaceus_, represented in Fig. 117, an

outline of the entire animal, the buccal apparatus being placed under

the shell, which has been broken in Fig. 116, so as to lay this organ

bare.

[Illustration: Fig. 116. Masticating apparatus of Echinus lividus.]

The shape of the _Clypeaster rosaceus_ is oval, straighter in front, and

thick and rounded at the edges. It is more common and more largely

distributed than any other living species, and it is supplied with four

or six ambulacra, or feet.

I never could understand why the dental framework of the sea-urchin has

been called Aristotle's Lantern, for this formidable apparatus resembles

the front view of a battery of cannon more than a lantern. It consists

of a series of pieces designated by the names of compass, scythe,

pyramid, and plumula, which it would serve no useful purpose to

describe.

[Illustration: Fig. 117. Clypeaster rosaceus (Lamarck).]

We have said that the mouth of the urchin is monstrous in proportion to

its size, and the teeth of proportionate dimensions. As these project

from a very formidable mouth, one can easily be assured of the sharpness

of their extremities by intruding his fingers on them. In fact, it is

necessary that these organs should be singularly powerful, because, as

we shall see farther on, the sea-urchin makes incisions in the solid

rock with them, and hollows out shelter for himself. The strong and

sharp teeth grow at the base in proportion as they are used at the

points, as is the case with some of the rodent mammalia. By this means

they are always sharp and in good condition. Five groups of powerful

muscles are used to work these terrible grinders.

To this formidable mouth is attached an œsophagus or gullet, and an

intestine which extends along the interior walls of the carapace,

describing the circumference of its principal contour.

The regimen of the Echinidæ is still imperfectly known; nevertheless,

from the presence of shells, fragments of corals, crustaceans, and even

other Echinodermata in their intestinal tube, it is to be inferred that

a certain number of them at least are carnassiers, or flesh-eaters,

while others are supposed on the same evidence to be vegetarians. The

organs of respiration of the Echinidæ appear to be certain flattened

vesicles in the form of very delicate laminæ, which adhere to the

internal surface of the walls of the body, and float freely in the

liquid with which the visceral cavity is filled. These organs, known as

the internal _branchiæ_, are in communication with the central canal and

ambulacral tubes. The heart is spindle-shaped, tapering above, swelling

below. There are two distinct vascular systems, one intestinal, the

other cutaneous.

[Illustration: Fig. 118. Skeleton and Masticating Apparatus.]

Their nervous system consists of a ring, which surrounds the gullet, and

is placed at a short distance from the mouth. In this ring the nervous

trunks have their origin. In relation to the senses, that of touch is

highly developed. Certain branching tentacula, which surround the mouth,

fashioned like nippers, and the ambulacral tentacles, are its principal

organs. They appear to be altogether destitute of organs of sight. It

has sometimes been argued that four or five red points at the summit of

the dorsal face are eyes; but this opinion has not been maintained, nor

has any crystalline lens been found in these spots to justify it.

Captain de Condé states that he examined a sea-urchin with long spears

in a pool of water, which he tried to catch, when he saw it direct its

flight towards his hand, all its defences being erect. Surprised at this

manœuvre, he tried to seize it from another quarter; its spines were

instantly directed to the other side. "I have thought from that time

that the urchin saw me, and prepared to resist my attack. In order,

however, to satisfy myself whether or not the movement in the water

caused by my approach might have produced the effect described, I

repeated the experiment with greater caution. But the creature always

directed its spines in the direction of the object which threatened it,

whether it was in the water or out of it." He satisfied himself that

these animals certainly could see, and that their spines served them as

a means of defence.

These wonderful spines, this calcareous envelope, this armour so

marvellously studded, with which nature has so bountifully provided the

Echinidæ, appear to have been insufficient, inasmuch as these very

spines, in order to secure the safety of the animal, are gifted with the

power of hollowing a dwelling for themselves out of solid rocks of the

hardest material, such as granite and sandstone. They fix themselves to

its surface by means of their tentacles; they make an incision by means

of their strong teeth, removing the débris with their spines as fast as

it is produced. When the hole is large enough, they entrench themselves

in it, with their spines and their threatening pikes levelled to protect

them from all external assaults. To M. Caillaud, the conservator of the

museum of Nantes, we are indebted for an excellent account of the manner

in which this buccal apparatus is made to operate. "The Lantern of

Aristotle," says this author, "forms the mandibullary apparatus; the

teeth are five in number, and they may as well receive the denomination

of a series of saws and picks as of teeth, for they are surprisingly

adapted to the excavation of holes in the hardest rock. These five picks

are about the eighth of an inch long, and they serve the sea-urchin at

once as masticators and excavating implements. In opening the jaws,

these five teeth strike the stone forcibly rather than scrape it." This

property of hollowing their dwelling out of the solid rock appears,

however, to belong to only a small number of the Echinidæ; most of them

are content to hide themselves under the stones, while the species

having the spines slender and the shell very thin bury themselves in the

sand, with which they cover themselves entirely, leaving only a small

hole to breathe through. The _Spatangus_, which is furnished with short

thick spines on the under part of its body, which spread out at the

extremity like the channel of a spoon, proceeds with its mining

operations as follows, according to Mr. Jonathan Franklin. "Figure to

yourself, reader, the animal on the sea-shore. He commences his

operations by turning the lower spines in such a manner as to form a

hollow on the sand bank, in which he sinks by his own weight; but as he

sinks, a great number of the spines are brought into action, throwing

up the sand with increased activity, while the sand thrown up, returning

again, soon covers the body of the worker, and he has soon buried

himself beneath the surface. In this situation the long hair-like spines

situated upon the back begin to play their part; they prevent the sand

from entirely covering the animal by forming a little round hole,

through which water is introduced to the mouth and respiratory organs."

The hiding-place of the sea-urchin is, however, easily detected in the

sand by the hole thus arranged for the respiration of the animal, and

the fishermen think they can predict storms according to the depth of

the hole.

The Echinidæ are reproduced by eggs, which are red and nearly

microscopic. As it issues from the egg the larva has the appearance of a

very minute fish. It is not at once converted into the perfect animal,

but undergoes a certain metamorphosis analogous to that of the

caterpillar into the butterfly. But, as we have already stated in

treating of the Asteriæ, it produces, at a certain stage, by some sort

of internal process of generation, a sea-urchin, which, being at first

only an organ of the larva, begins to live an independent life when the

nursing larva has destroyed itself. The manner in which the urchin

unfolds itself at the expense of the larva is quite analogous to that

which the asterias present: it is another case of alternate generation,

of which our space does not permit us to give even a general outline.

Sea-urchins are found in every sea; they dwell in sandy bottoms, and

sometimes upon rocky ground. They are caught with wooden pincers when in

shallow water; when found at the water's edge, they may be taken by a

gloved hand.

The urchin, like the crab, which it also resembles in taste, becomes red

when boiled; only certain species are comestible, however. In Corsica

and Algeria the Melon-shaped Urchin (_Echinus melo_) is much esteemed.

In Naples and in the French ports of the Channel the _Echinus lividus_

is eaten. In Provence the Common Sea-urchin (_Echinus esculentus_ and

_Echinus granulosus_) are the favourites.

Sea-urchins are eaten raw like oysters. They are cut in four parts, and

the flesh taken out with a spoon; they are sometimes, but more rarely,

dressed by boiling, and eaten from the shell like an egg, using long

sippets of bread: hence the name of sea-eggs, which they bear in many

countries.

[Illustration: Plate IX.--Sea Urchins lodged in the rocks they have

excavated.]

Sea-eggs were a choice dish upon the tables of the Greeks and Romans;

they were then served up with vinegar or hydromel, with the addition of

mint or parsley. When Lentulus feasted the priest of Mars--the Flamen

Martialis--this formed the first dish at supper. Sea-eggs also appeared

at the marriage feast of the goddess Hebe. "Afterwards," says the poet,

"came crabs and sea-urchins, which do not swim in the sea, but content

themselves by travelling on the sandy shore." For my own part, I have

only once partaken of sea-urchin, and it appeared to me to be food fit

for the gods; but perhaps the circumstances sufficiently explain this

dash of culinary enthusiasm. The Reserve Restaurant at Marseilles has

not always been the vast stone edifice we now behold, backed

majestically by the mountain, and fronting the sea on the promenade of

the Corniche du Prado. In 1845 it rose quite at the entrance of the

port, a small glass cage, suspended as it were by a magic thread between

the heavens and the sea. From this aërial dwelling, overhanging with

unheard-of audacity the waters which surrounded it on all sides, we

gazed on the most wonderful prospect in the world, and reposed ourselves

while enjoying this intoxicating scene, during which the ships were

continually entering the port, passing under our very feet. It was in

this enchanted palace that sea-urchins were served up, supported by the

traditional bouillabaise.

As I have said, it appeared to me delicious. Was it the Provençal dish,

the savoury bouillabaise, which contributed to my appreciation of the

humble sea-urchin of the Mediterranean? Was not the marvellous view

which I enjoyed from the heights of my empyreum of glass the indirect

cause of it? This is a tender and charming problem which I love to leave

floating in the clouds, half evanescent, of my youthful recollections.

HOLOTHURIA.

The ignorant, like you and I, call the Holothuria the Cornechou, or

Sea-cucumber, and perhaps, for two reasons, they are not far wrong. The

term sea-cucumber expresses with wonderful exactness the shape of the

animal, and its habitation, the sea; and, again, it would puzzle the

most learned to explain the word _Holothuria_. The body of this strange

creature presents the form of an elongated and worm-like cylinder; its

dimensions are so variable that, while some species are only an inch or

two in length, others attain thirty and even forty. In general, the skin

of the Holothuria is thick and leathery; it includes muscles, and is

armed occasionally with small projecting hooks or fangs, which enable

the creature to hang for a few seconds on to foreign bodies. From this

coriaceous envelope issue tentacular feet analogous to those described

in the sea-urchin and sea-star.

When we open a Holothuria we find nearly the whole internal cavity

occupied with little white tubes. We know that the fabulous cucumber

spoken of in the "Arabian Nights" was stuffed with pearls by the

talking-bird. With our poor animal this, alas! is not so. These are no

pearls, but simple prosaical tubes containing the ova. The mouth opens

at the extremity of the body; it forms a sort of funnel, and is

surrounded, as by a glory, with an elegant circle of tentacula. In the

living animal, when it feels itself in security, these tentacles expand

themselves like the corolla of a flower. When the fisherman seizes a

Holothuria in the water this crown of tentacles ceases to appear, for

the animal has the power of withdrawing it quite suddenly, and now it

resembles nothing so much as a common leech. If, however, it is

preserved in fresh sea-water and left in peace--if we treat it, in

short, with the regard due to its elegant crown of tentacula--this

elegant ornament will be expanded in all its glory. Immediately below

the mouth is a muscular pharynx, which is contained in a long intestine,

with many convolutions, which terminate in the posterior part of the

body in an orifice whence is thrown from time to time a little jet of

water. The terminal portion of the intestinal canal in these animals is

enlarged, introducing us to a system of numerous tubes which branch off

into the visceral cavity, receiving the water from without while

breathing by its posterior extremity; the animal can at will fill this

reservoir or eject the water, and it is by these alternate movements of

aspiration and its reverse that it renews the oxygen necessary for

respiration. The circulation appears to form a complete circle, there

being no heart or central agent; but a ring round the gullet, from which

issue five principal nervous chords, represents the nervous system.

The Holothurias are of separate sexes, and they differ from the

sea-urchins and asterias in this: that their larvæ are converted bodily

into a young Holothuria without losing their organs. The bodies of

certain species are lubricated by an acrid and corrosive liquid: thus

_H. oceania_, described by Lesson, which is about forty inches in

length, secretes at the surface of its body an irritating fluid, which

produces an intolerable itching in the finger which touches it. Nor can

the inhabitants of the South Sea Islands look at it without loathing.

Fig. 119 represents _H. lutea_, or the _Stychopus luteus_ of Brandt, who

describes as its distinctive character three rows of tentacular feet on

the ventral surface.

[Illustration: Fig. 119. Holothuria lutea (Quoy and Gaimard).]

We have spoken of the strange suicidal tendency of the sea-stars: the

Holothuria exhibits the same phenomena, but, having no brittle envelope

like the asterias, it cannot break itself into bits in the presence of

its disconcerted enemy; but kills itself in this manner: having some

cause of grief and trouble--such, for instance, as the attack of an

enemy or the pursuit of some fisherman--by a sudden and unexpected

movement it ejects its teeth, its stomach, its digestive apparatus, and

reduces itself to a simple empty membranous sac, with an unfurnished

mouth; and, as a singular fact, this empty sac still shrinks and

contracts in the hand which grasps it. It must be admitted that this is

a strange mode of evading its enemies: the soldier rarely throws his

arms away in the moment of danger! But the Holothurias possess a

wonderful recuperative power also; and it is probably quite conscious,

when it thus empties itself to disappoint its pursuer, that it can

promptly replace the organs which it has voluntarily parted with.

Dr. Johnston relates that he had forgotten for some days to supply a

Holothuria with a change of water. The creature, in consequence, ejected

its tentacles, its buccal apparatus, digestive tubes, and a portion of

its ovaries. Still it was not dead, but was sensible to the least

movement, and lived to reproduce all its organs anew.

Not only do the Holothurias eject their organs and afterwards renew

them, but they divide themselves spontaneously into two portions. Their

two extremities are first enlarged; then their middle parts gradually

become straight, like a thread: finally, this thread breaks, and each

separate part of the animal becomes a perfect Holothuria. It has been

cut into two pieces, and each of these species becomes a new being.

[Illustration: Plate X.--Fishing for and curing the Holothuria in the

Indian Ocean.]

The habits of these animals are but little known. They inhabit the seas,

and are spread over every latitude. Their very limited movements consist

in a kind of reptation or crawling motion, produced by the undulations

of their bodies or by the contractions of their feet. Holothurias are

generally found in the act of creeping upon stones or on portions of

submarine rock, but always in sheltered places, for they appear to dread

the action of light. They sometimes find themselves caught by fishermen

in their nets. If held in the hand they contract, their bodies become

hard and rigid, and the sea water with which they are filled is ejected

with force. We need not add that fishermen reject with disdain the

Holothurias taken in their nets; the sea-cucumber has never been thought

worthy of a place on our tables. Truth is on this side, error on that,

is a maxim as true in morals as in cookery. The sea-cucumber, which

Europeans disdain, is a favourite dish among the Chinese. The fishery,

preparation of, and transport of these animals to market, plays an

important part in the commerce and industry of the East. One rather

large species, the _Holothuria tubulosa_, in which, by-the-bye, a

singular parasite fish (_Fierasfer fontanesii_) lives, is common in the

Mediterranean. This species is eatable, and much relished at Naples. In

the Ladrone Islands _Holothuria guamensis_ is preferred. But nowhere is

it esteemed of such importance as in the Malayan and Chinese seas. In

these countries, and on most of the shores of the Indian Ocean, the

_Holothuria edulis_, vulgarly called _Trepang_, is eaten with delight.

Thousands of junks are annually equipped for the Trepang fisheries. The

Malay fishermen carry to this fishery a degree of patience and dexterity

truly remarkable. Lying down in the fore part of their vessels, and

holding in their hands a long bamboo, terminating in a sharp hook, their

eyes, accustomed to this fishing, frequently discover the animal at a

distance of not less than thirty yards, as it creeps along the surface

of the submarine rocks or corals. The fisher darts his harpoon at this

distance, and seldom misses his prey. When the water is shallow, that is

to say, not more than four or five fathoms deep, divers are sent down to

obtain these culinary monsters, who seize them in their hands, and in

this manner can take five or six at a time. To prepare the fish and

preserve them for transport to the markets, the Malay and Chinese

fishermen boil them in water, and flatten them with stones. They are

then spread out on bamboo mats to dry; first in the sun, and then by

smoking them. Thus prepared, they are enclosed in sacks, and shipped to

the Chinese ports, where they are particularly esteemed. This fishery

takes place in the months of April and May.

In his voyage to the South Pole, Captain Dumont d'Urville, in traversing

the Chinese seas, had an opportunity of assisting at this fishery, which

he has described very graphically. We quote the passage in which the

French navigator relates what he witnessed at this curious scene. While

the ships were lying quietly at anchor, "we saw," he says, "entering the

bay, four Malay proas, bearing Dutch colours, which dropped their

anchors about a cable's length from Observatory Islet. The padrones or

captains of these vessels soon presented their salutations, and informed

me that they had started from Macassar at the end of October, with the

western monsoon, and that they came to fish for Holothuria (trepang)

along the coasts of New Holland, from Melville Island to the Gulf of

Carpentaria, where the east wind met them and assisted their return,

when they revisited all the points of the coast, anchoring in every bay

where they hoped to find fish. We were in the first days of April; the

east monsoon was definitively established; the Malay fishermen were

returning in their circuit, and, in passing, they came to exercise their

industry in Raffles' Bay. An hour after their arrival they were all at

work, and the laboratory for the preparation of their fish was

established within our view. The roadstead had no longer the aspect of a

vast solitude: wreaths of smoke crowned the summit of Observatory

Island, where, as if by enchantment, several large sheds had sprung up,

while numerous vessels, supplied with divers, were proceeding to fish

for Holothurias, which were passed immediately to the furnaces erected

for curing them. In the course of my voyage I have often remarked little

walls constructed of dry stones, consisting of several half-circles

joined one to the other. I had often, but vainly, tried to discover the

use of these little structures: I was now enlightened. The Malays

arrived. Their boats were scarcely anchored when several large boilers,

in the shape of a half-sphere, the diameter of which might be about

forty inches, were placed upon the stone walls of which I have spoken,

and now served as improvised furnaces. Near to them are sheds, composed

of four strong posts driven into the earth, supporting roofing covered

with hurdles, on which it is probably intended to dry the Holothurias.

During their sojourn in this bay, the fishermen, having fine weather,

made no use of these sheds, having probably only prepared them as a

precaution.

"A crowd of men actively employed in establishing their laboratories

gave an unaccustomed appearance to the bay, which could not fail to

attract the savage inhabitants of the main land. Very soon, indeed, we

could see them hastening from all sides, and nearly all reached the

little island, either by swimming or wading through the sheet of shallow

water which separates it from the main land. I only saw one pirogue,

made of the bark of a tree badly put together, which gave a passage to

three of these visitors. When night arrived, the Malays had finished all

their preparations; some of them remained to guard what they had left on

shore, all the others returned to their boats.

"In the interval, a boat from the Astrolabe being wanted to carry some

visitors from the island, I profited by the occasion to visit one of

the proas, accompanied by M. Roquemauel. We were received with much

politeness, and even cordiality, by the captain or padrone of the boats.

He showed us over his little ship. The keel appeared to us sufficiently

solid; even the lines did not want elegance; but great disorder seemed

to reign in the stowage department. From a kind of bridge, formed by

hurdles of bamboos and junk, we saw the cabin, which looked like a

poultry-house; bags of rice, packets, and boxes were huddled together.

Below was the store of water, of cured trepang, and the sailors' berths.

Each boat was furnished with two rudders, one at each end, which lifted

itself when the boat touched the bottom. The craft was furnished with

two masts, without shrouds, which could be lowered on to the bridge at

will by means of a hinge; they carry the ordinary sail; the anchors are

of wood, for iron is rarely used by the Malays; their cables are made of

ratan fibre; the crew of each bark consists of about thirty-seven, each

shore-boat having a crew of six men. At the moment of our visit they

were all occupied in fishing operations, some of them being anchored

very near to us. Seven or eight of their number, nearly naked, were

diving for trepang; the padrone alone was unoccupied. An ardent sun

darted his rays upon their heads without appearing to incommode them, an

exposure which no European could hold up under. It was near mid-day, and

the moment, as our Malay captain assured us, most favourable for the

fishing. In fact, we saw that each diver returned to the surface with at

least one animal, and sometimes two, in his hands. It appears that the

higher the sun is above the horizon, the more easily is the creature

distinguished at the bottom. The divers were so rapid in their

movements, that they scarcely touched the boat, into which they threw

the animals, before they dived again. When the boat was filled with

them, it proceeded to the shore, and its place was supplied by an empty

one. I followed one of these, to witness the process of curing which

they adopted.

"The Holothuria of Raffles' Bay is from five to six inches long and

about two in diameter; it is a gross fleshy mass, somewhat cylindrical

in form, but no external organ is visible. The mollusc glues itself to

the rocks at the bottom of the sea, and, as it can only move very

slowly, the Malay divers seize it readily. The greatest merit of a

fisherman is to have a practised eye, to distinguish the animal at the

bottom, and to dive directly to the spot where it lies. To preserve

them, the fishermen throw them, while still living, into a cauldron of

boiling sea water, where they are stirred about by means of a long pole,

which is supported upon another pole fixed in the earth, but having a

forked end, which acts as a lever. In this process the trepang gives up

all the water it contains, and is withdrawn at the end of two minutes. A

man armed with a large knife now extracts the entrails, and it is thrown

into a second cauldron, having only a small quantity of water, seasoned

with mimosa bark. The object of this second operation is to smoke the

animal in order to preserve it the better, for the bark is consumed in

the process. The trepang is now placed upon hurdles and dried in the

sun. When sufficiently dried, it is stowed away in the hold of the proa.

"It was about two o'clock in the afternoon when the divers ceased their

labours and came ashore. My tent was soon surrounded. I recognized the

captain of the proa among those who had previously visited me. He

approached and examined all the instruments used in the Observatory with

great attention, seeking to discover their use. I showed him a gun with

percussion cap, which astonished him greatly, especially when I pointed

out to him its great superiority over the flint-lock. He assured me that

these arms were still unknown in the Celebes, his country; but he failed

to convince me of that. He questioned me as to the places we had

visited, and where we were going. I endeavoured to sketch a map of New

Holland, New Zealand, and New Guinea upon a leaf. He then took my

pencil, and added to it the Indian Archipelago, the coasts of China and

Japan, and the Philippine Islands. Surprised in my turn, I asked him if

he had visited all these places. He replied in the negative; but added

that he knew their position perfectly, and could easily take his vessel

to any of them. Finally, the interview terminated by his asking for a

glass of arrack. I do not know if this intelligent Malay professed the

Mahometan religion, but I do know that he drank half a bottle of wine

and a quarter of a pint of arrack without being at all the worse for it.

He then offered me some prepared trepang, inviting me to taste it, which

I did; to me it appeared to resemble the lobster in taste. My men liked

it, and thankfully accepted the captain's offer; for my part, I felt an

utter repugnance even to taste it.

"According to the account I had from the Malay captain, the price of

trepang in the Chinese markets was fifteen rupees, about thirty

shillings the pekoul, or a hundred and twenty-five pounds. He

estimated his cargo to be worth about a hundred and twenty pounds. The

fishing had occupied him and his crew three months. From the earliest

times this commerce has belonged exclusively to the Malay fishermen, and

it will always be difficult for Europeans to compete with them. The

Malay vessels are equipped on the most economical principle, and the men

are wanting neither in sobriety, intelligence, or activity.

[Illustration: Plate XI.--Synapta Duvernæa. (Quatrefages.)]

"It was nearly four o'clock when the Malays finished their operations.

In less than half an hour they had embarked their cargo; the tents were

struck, and, together with the boilers, carried back to the boats, which

were already preparing to set sail. At eight o'clock in the evening they

hoisted sail and left the bay."

Some idea may be formed of the extent and importance of the Holothuria

fishing by the number of ships which it attracts in this part of the

East. Captain King assures us that two hundred vessels annually leave

Madagascar to fish for the _sea slug_, as it is sometimes called.

Captain Flinders, being on the coast of Australia, learnt that a fleet

of sixty vessels, having a hundred men on board, had left Madagascar two

months previously in the same pursuit.

Among the Holothurias, one particular genus, the _Synapta_, is

distinguished from others of the family by the absence of the ambulacral

feet, and by the fact of its uniting both sexes in one individual. This

remarkable Echinoderm, _Synapta duvernæa_, is represented in PL. XI. M.

Quatrefages, who discovered it in the Channel, gives the following

description of it in his great work, "Le Souvenirs d'un Naturaliste."

"Imagine," he says, "a cylinder of rose-coloured crystal, as much as

eighteen inches long and more than an inch in diameter, traversed in all

its length by five narrow ribbons of white silk, and its head surmounted

by a living flower, whose twelve tentacles of purest white fall behind

in a graceful curve. In the centre of these tissues, which rival in

their delicacy the most refined products of the loom, imagine an

intestine of the thinnest gauze gorged from one end to the other with

coarse grains of granite, the rugged points and sharp edge of which are

perfectly perceptible to the naked eye.

"But what most struck me at first in this animal was, that it seemed

literally to have no other nourishment than the coarse sand by which it

was surrounded. And then when, armed with scalpel and microscope, I

ascertained something of its organisation, what unheard-of marvels were

revealed! In this body, the walls of which scarcely reach the sixteenth

part of an inch in thickness, I could distinguish seven distinct layers

of tissue, with a skin, muscles, and membranes. Upon the petaloid

tentacles I could trace terminal suckers, which enabled the Synapta to

crawl up the side of a most highly polished vase. In short, this

creature, denuded to all appearance of every means of attack or defence,

showed itself to be protected by a species of mosaic, formed of small

calcareous shield-like defences, bristling with double hooks, the points

of which, dentated like the arrows of the Caribbeans, had taken hold of

my hands."

If one of these Synapta is preserved alive in sea-water for a short

time, and subjected to a forced fast, a very strange phenomenon will be

observed. The animal, being unable to feed itself, successively detaches

various parts of its own body, which it amputates spontaneously. A great

compression or ring is first formed, and then the separation of the

condemned part takes place quite suddenly. "It would appear," says M.

Quatrefages, "that the animal, feeling that it had not sufficient food

to support its whole body, was able successively to abridge its

dimensions, by suppressing the parts which it would be most difficult to

support, just as we should dismiss the most useless mouths from a

besieged city."

This singular mode of meeting a famine is employed by the Synapta up to

the last moment. After a few days, in fact, all that remains of the

animal is a round ball, surmounted by its tentacles. In order to

preserve life in the head, the animal has sacrificed all the other parts

of its body.

In order to find natural novelties--to find unforeseen subjects of study

and reflection, it is not necessary to run over the world or travel

great distances. It is only necessary to visit the banks of the nearest

river, or descend to the sea shore, and leave the sea to reveal a

fragment of the marvels which it conceals in its bosom.

MOLLUSCA.

The class Mollusca--pulpy animals--forms a grand division which man has

been pleased to make in the animal kingdom, and immediately below the

Vertebrata and above the Annulosa, which again stand above the

Coelenterata, which includes the polyps, sea-anemones, hydras, and

corals, which last are more highly organized than the Protozoa.

[Illustration: Fig. 120. P. C. Mollusca.]

The Mollusca may be divided into two groups, the Mollusca proper and the

Molluscoïda. The mollusc proper, as represented in Fig. 120, presents

the following parts, and is supposed to be bilaterally symmetrical, H,

is the hæmal parts, in which the heart is situated, commonly called the

dorsal part, although the word is used in a different sense in different

divisions of the animal kingdom. In the same manner the opposite region

(N) is not termed the ventral, but the neural part, in philosophical

anatomy. It is the region in which the great centres of the nervous

system are placed. The termination (_a_) is the anterior or oval part;

the other end (_b_), the posterior or anal part: between these

extremities the intestines take a straight course. The neural surface

is that upon which the majority of molluscs move, and by which they are

supported, and it is commonly modified to subserve these purposes by the

formation of a muscular expansion or disk, called the foot. Three

regions, in many genera very distinctly divided from one another, may be

distinguished in this foot: an anterior, the _Propodium_ (_p p_); a

middle, the _Mesopodium_ (_m s_); and a posterior, the _Metapodium_ (_m

t_). In addition to these, the upper part of the foot, or middle portion

of the body, may be prolonged into a muscular enlargement on each side,

just below the junction of the hæmal with the neural region, the

_Epipodium_ (_e p_). The mass of the body between the foot proper and

the part of the abdomen which bears the epipodium may be termed the

mid-body, or _Mesosoma_. On the upper part of the sides of the head are

two pairs of organs, namely, the eyes and tentacles. In the hæmal region

the integument may be modified and raised up into a fold at the edges,

either in front or behind the anus. When so modified, it is called a

mantle, _Pallium_. In front of the anus again, the _branchiæ_ (_t_)

project as processes of the hæmal region. Among the internal organs, the

heart (_u v_) lies in front of the branchiæ in the hæmal regions, the

nervous ganglia (_x_ _y_ _z_), of which there are three principal pairs,

being arranged around the alimentary canal, which they encircle.

Such is the general type of the class Mollusca, of which, however, the

variations are innumerable. They are all soft-skinned animals, without

either articulated exterior or annular external skeleton. Their nervous

system, being without cerebro-spinal axis, is entirely composed of

ganglions, which are all reunited in the oesophagus without constituting

in any case a lengthened median chain. Their digestive organs are

complete--that is, they are provided with two apertures; their principal

organs are symmetrical and according to a plan, usually curving, by

which their bodies are divided into two parts.

The first series or subdivision, to which Milne Edwards has given the

name of _Molluscoïda_, includes under that term the Bryozoaires,

Ascidians, and Tunicata.