While the sessile Ascidiæ remind one of the polyps, the transparent

Salpæ, freely swimming in the sea, bear a great resemblance to the

pellucid jelly-fishes. Each resembles a crystalline tube, through

which one can distinctly see the internal coloured parts. Sometimes

these animals, which abound in the warmer seas, are found solitary,

at other times associated in circular or lengthened groups, termed

garlands, ribands, and chains; but, strange to say, these two forms so

different in outward appearance are only the alternating generations

of one and the same animal. The chained Salpæ produce only solitary

ones, and the latter only chains, or, as Chamisso, to whom we owe the

discovery of this interesting fact, expresses himself, "a salpa mother

never resembles her daughter, or her own mother, but is always like her

sister, her grand-daughter, or her grand-mother." When Chamisso first

made known his discovery, he was laughed at as a fanciful visionary, but

all later observations have not only fully confirmed his statement but

also discovered similar or even more wonderful metamorphoses among the

jelly-fish, polyps, crustacea, sea-urchins, and other marine animals.

Thus Chamisso gave the first impulse to a whole series of highly

interesting observations, and his rank is now as well established among

naturalists as it has long been among the most distinguished poets of

Germany. The Salpæ progress by the alternate contractions and dilatations

of their tubular body. In this manner the chains, as if obeying a common

impulse, glide along with a serpentine movement, and are often regarded

by sailors as sea-snakes.

[Illustration: Inner or under side of the superior plated surface of

Chelyosoma Macleayanum.

_a._ Branchial orifice.

_b._ Anal orifice.

_c._ Muscles bordering the carapace-plates.

_d._ Central hexagonal plate.

_e._ Surrounding plates.

_f._ The nerve-ganglion and nerve-fibres.

_g_, _h_. Auditory apparatus.

_i._ Row of tentacles, anterior to the œsophagus.

_j._ Stomach.

_k._ Part of the intestine.

]

Before quitting the Tunicata, a few points of interest in their simple

history remain to be noticed. Despite their humble organisation, they

have a heart which, as may easily be ascertained in the transparent

species, is subject to strange alternations of action. For after

having received for a minute or two the blood _from_ the branchiæ, and

propelled it _to_ the system at large, it will at once cease to pulsate

for a moment or two, and then propel the blood _to_ the branchial sac,

receiving it at the same time _from_ the system generally. After this

reversed course has continued for some time, another pause occurs,

and the first course is resumed. It is very probable that many of the

Tunicata are able to hear and to see. In Chelyosoma, organs have been

discovered whose structure seems to indicate that they are destined

for the transmission of sound, and the Ascidiæ have frequently around

the extremity of their tubes a row of coloured points similar to the

imperfect organs of sight present in the majority of the bivalve

Acephalans. Thus a closer examination of the lower animals is constantly

bringing new faculties to light, and the further we penetrate into the

secrets of their life the more we find occasion to admire the power and

wisdom of their Maker!

CHAP. XVI.

ECHINODERMATA.

STAR-FISHES, SEA-URCHINS, AND SEA-CUCUMBERS.

The Star-Fishes.--Their Feet or Suckers.--Voracity of

the Asterias.--The Rosy Feather-Star.--Brittle and

Sand-Stars.--The real Sea-Stars of the British Waters.--The

Sea-Urchins.--The Pedicellariæ.--The Shell and the Dental

Apparatus of the Sea-Urchin.--The Sea-Cucumbers.--Their strange

Dismemberments.--Trepang-fishing on the Coast of North Australia.--In

the Feejee Islands.

"As there are stars in the sky, so are there stars in the sea," is

the poetical exordium of Link's treatise on Star-fishes, the first

ever published on the subject; and James Montgomery tells us in rather

bombastic style, that the seas are strewn with the images of the

constellations with which the heavens are thronged.

This is no doubt highly complimentary to the star-fishes, but is far

from being merited by any particularly shining or radiant quality; as

they occupy a very inferior grade among the denizens of the sea, and

merely owe their stellar name to their form, which somewhat resembles the

popular notion of a star.

But if they are of an inferior rank to most marine animals; if even the

stupid oyster boasts of a heart, which they do not possess; yet a closer

inspection of their organisation shows us many wonderful peculiarities,

and proves to us once more that nature has impressed the stamp of

perfection as well upon her lowest and most simple creations, as upon

those beings that rank highest in the scale of life.

Every one knows the common Star-fish, with its lanceolate arms; its

generally orange-coloured back, thickly set with tubercles, and the pale

under-surface, with its rows of feet, feelers, or suckers, which serve

both for locomotion and the seizure of food.

When one of these creatures is placed on its back, in a plate filled

with sea-water, it is exceedingly curious to watch the activity which

those numberless sucking feet display. At first the star-fish is

motionless; for, offended by the rough handling it has undergone, the

feet have all shrunk into the body; but soon they are seen to emerge

like so many little worms from their holes, and to grope backwards and

forwards through the water, evidently seeking the nearest ground to lay

hold of. Those that reach it first immediately affix their suckers, and,

by contracting, draw a portion of the body after them, so as to enable

others to attach themselves, until, pulley being added to pulley, their

united power is sufficient to restore the star-fish to its natural

position.

[Illustration: Star-Fish.

The upper tuberculated surface is shown, with some of the spines of

the under surface projecting at the sides of the rays. At one of the

angles between the rays, on the right side, is seen the eccentric

calcareous plate, or madreporic tubercle, which indicates the

existence of a bilateral symmetry.]

This act of volition is surely remarkable enough in so simple an animal,

which scarcely possesses the rudiments of a nervous system, but the

simple mechanism by which the suckers are put into motion is still more

wonderful. Each of these little organs is tubular, and connected with

a globular vesicle filled with an aqueous fluid, and contained within

the body of the star-fish immediately beneath the hole from which the

sucker issues. When the animal wishes to protrude its feet, each vesicle

forcibly contracts, and, propelling the fluid into the corresponding

sucker, causes its extension; and, when it desires to withdraw them,

a contraction of the suckers drives back the fluid into the expanding

vesicles. The internal walls of the suckers and their vessels are

furnished with vibratory cilia, and by this simple means a continual

circulation of the fluid they contain goes on within them.

[Illustration: Lily-Encrinite.]

Numerous species of star-fishes are so very common in our waters,

that in many places the sea-bottom is literally paved with them. They

likewise abounded in the primeval ocean, for deep beds of carboniferous

limestone and vast strata of the triassic muschelkalk are often formed

by the accumulation of little else than the skeletons of Encrinites and

Pentacrinites, which, unlike the sea-stars which every storm drifts

upon our shores, did not move about freely, but were affixed to a

slender flexible stalk, composed of numerous calcareous joints connected

together by a fleshy coat. The feathered bifurcated arms of the Crinoids

are unprovided with suckers, which would have been perfectly useless

to creatures not destined to pursue their game to any distance, but

passively to receive the nutriment which the current of sea-water set

in motion by their richly-ciliated pinnules conveys to the mouth. These

beautiful creatures were formerly supposed to be nearly extinct, for up

to within the last few years only two living stalked crinoids were known

in the ocean of the present period, but the dredge has latterly brought

up new and remarkably fine species from depths of more than 2000 fathoms,

and there is every reason to believe that these animals still form an

important element in the abyssal fauna.[S]

[Footnote S: See page 420.]

[Illustration: Portion of the Pentaorinus Briareus. (Fossil.)]

Of freely-swimming Crinoids but one single representative is known in the

northern seas, the Rosy Feather-star (_Comatula rosacea_), whose long

and delicately fringed rays and deep rose colour dotted with brown may

serve to give us an idea of the beauty of the submarine landscapes where

_Pentacrinus Wyville-Thomsoni_ or _Bathycrinus gracilis_ abound. During

the earlier stage of its existence, the comatula is attached to a stalk;

a discovery for which science is indebted to Mr. T. V. Thompson, who in

1823 dredged in the Cove of Cork a singular little pedunculated crinoid

animal (_Pentacrinus europæus_), which he found attached to the stems

of zoophytes. It measured about three-fourths of an inch in height, and

resembled a minute _comatula_ mounted on the stalk of a _pentacrinus_.

When this pygmy representative of the ancient lily-stars was first

dragged up from its submarine haunts, it created a great sensation among

naturalists, as it was the first recent animal of the encrinite kind

which had ever been seen in the seas of Europe. At first it was supposed

to be a distinct species, but Mr. Thompson, by carefully following it

through all the stages of its growth, succeeded in proving that it was

merely the hitherto unnoticed young of the rosy feather-star.

This elegant crinoid is found all round our coasts, and its range

extends from Norway to the shores of the Mediterranean. In swimming, the

movements of its arms exactly resemble the alternating stroke given by

the medusa to the liquid element, and have the same effect, causing the

animal to raise itself from the bottom and to advance back foremost, even

more rapidly than the medusa. When dying, either in fresh water or in

spirits, it emits a most beautiful purple colour, which tinges the liquid

in which it is killed.

The _Ophiuridæ_, or _snake-stars_, are essentially distinguished from

the true _star-fishes_ by the long serpent or worm-like arms, which are

appended to their round, depressed, urchin-like bodies. They have no true

suckers with which to walk, their progression being effected (and with

great facility) by the twisting or wriggling of their arms, which are

moreover in many species furnished with spines on the sides, assisting

locomotion over a flat surface. These arms are very different from those

of the true star-fishes, which are lobes of the animal's body, whereas

the arms of the Ophiuridæ are mere processes attached or superadded to

the body.

These animals are very generally distributed through the seas of our

earth, both of its northern and southern hemispheres, but are found

largest in the tropical ocean. In our own waters they are very abundant,

and are among the most curious and beautiful game pursued by the dredger.

[Illustration: Sand-star.]

The British Ophiuridæ belong to two generic types, that of the

_Ophiuræ_ and that of the _Euryales_. The former, to which the sand and

brittle-stars belong, have simple arms; the latter, arms ramifying into

many processes.

The rays of the Sand-stars have a whip-like or lizard-tail appearance,

while those of the Brittle-stars look like so many centipedes or

annelides attached at regular distances round a little sea-urchin. We

have ten native brittle-stars, the most common of which (_Ophiocoma

rosula_, Forbes) is also one of the handsomest, presenting every variety

of variegation, and the most splendid displays of vivid hues arranged in

beautiful patterns. Not often are two specimens found coloured alike. It

is the most brittle of all brittle-stars, separating itself into pieces

with wonderful quickness and ease. Touch it, and it flings away an arm;

hold it, and in a moment not an arm remains attached to the body. "The

common brittle-star," says Edward Forbes, "often congregates in great

numbers on the edges of scallop-banks, and I have seen a large dredge

come up completely filled with them; a most curious sight, for when the

dredge was emptied, these little creatures, writhing with the strangest

contortions, crept about in all directions, often flinging their arms in

broken pieces around them; and their snake-like and threatening attitudes

were by no means relished by the boatmen, who anxiously asked permission

to shovel them overboard, superstitiously remarking that the things

weren't altogether right."

Fancy the naturalist's vexation, who has no other means of preserving a

brittle-star entire than by quickly plunging it into cold fresh water,

which acts as a poison on the Ophiuræ as well as on most other marine

animals, and kills them so instantaneously that even the most brittle

species have no time to make the contraction necessary to break off their

rays.

The _Ophiocoma rosula_ seems to be equally abundant on all parts of the

coast of Britain and Ireland. It is fond of rocky places, and grows in

Shetland to a much larger size than elsewhere. It is said to prey on

little shells and crabs, and is greatly relished by the cod in its turn,

great numbers being often found in the stomach of that voracious fish.

[Illustration: Warted Euryale.]

The Scotch or Shetland Argus (_Euryale verrucosum_, Lamarck), a very rare

animal, of which the adjoining wood-cut represents a segment, is the only

British _Euryale_. It measures a foot or more across, and its singular

aspect has long excited admiration among naturalists. "So odd a creature

as this," remarks Bradley in his "Works of Nature," "is well worth the

contemplation of such curious persons as live near the sea, where every

day they have subjects enow to employ their curiosity and improve their

understanding." Grew says that "as he swims he spreads and stretches out

all his branches to their full length, and so soon as he perceives his

prey within his reach, he hooks them all in, and so takes it as it were

in a net."

The British species of true star-fishes may be arranged under four

families. The _Urasters_ are distinguished from all others by having four

rows of suckers in each of the avenues which groove the under surface of

their rounded rays. In consequence of the great number of these singular

organs, the under surface of a living cross-fish presents a sight

truly curious and wonderful. Hundreds of worm-like suckers, extending

and contracting, coiling and feeling about, each apparently acting

independently of the others, give the idea rather of an assemblage of

polypi than of essential parts of _one_ animal. They are sensitive in the

extreme, for, if we touch one of those singular tubes when outstretched,

all those in its neighbourhood are thrown into a state of agitation;

and when it shrinks from our touch, changing from a lengthy fibre to a

little shrunk tubercle, some of its neighbours, as if partaking in its

fears, contract themselves in like manner.

[Illustration: Common Cross-fish.]

The common Cross-fish (_Uraster rubens_) abounds on most parts of our

shores, so as in some places to be used for manure in large quantities.

"It is a sworn enemy to oysters, and as it is frequently found with one

or more of its rays broken off, the fishermen fancy that it loses them

in consequence of its oyster-hunting propensities; that it insinuates an

arm into the incautious oyster's gape, with the intent of whipping out

its prey, but that sometimes the apathetic mollusk proves more than a

match for its radiate enemy, and closing on him, holds him fast by the

proffered finger; whereupon the cross-fish preferring amputation and

freedom to captivity and dying of an oyster, like some defeated warrior

flings his arms away, glad to purchase the safety of the remaining whole

by the reparable loss of a part, as it has the power of reproducing the

broken rays.

"There is, however, reason to think that the cross-fish destroys his prey

in a very different manner from that just narrated; for star-fishes are

not unfrequently found feeding on shell-fish, enfolding their prey within

their arms, and seeming to suck it out of its shell with their mouths,

pouting out the lobes of the stomach, which they are able to project in

the manner of a proboscis. Possibly the stomach secretes an acrid and

poisonous fluid, which, by paralysing the shell-fish, opens the way to

its soft and fleshy parts."--_Forbes's Star Fishes._

The _Solasters_ are "suns in the system of sea-stars," and are entitled

to this distinguished rank among the marine constellations by their many

rays and brilliant hues. The _Solaster papposa_, or common Sun-star, with

rays varying in number from twelve to fifteen, is one of the commonest,

and at the same time handsomest, of all the British species. Sometimes

the whole upper surface is deep purple, and frequently the disk is red,

and the rays white tipped with red. It grows to a considerable size,

having been found eleven inches broad.

The Goniasters, or Cushion-stars, are distinguished from the allied

species by their pentagonal form. One of the most singular of our native

species is the Birdsfoot Sea-star (_Palmipes membranaceus_), being the

thinnest and flattest of all its class. When alive it is flexible, like

a piece of leather, and a person who had never seen it before would be

apt to mistake it for the torn off dorsal integument of some gibbous

goniaster. The colour is white, with a red centre and five red rays,

proceeding one to each angle. The whole upper surface is covered with

tufts of minute spines arranged in rows.

The Asteriæ, with their stellate body and flat rays, are very different

in aspect from the Goniasters. The Butt-thorn (_Asterias aurantiaca_)

owes its name to one of those strange superstitions which originate in

some inexplicable manner, and are handed down by one credulous generation

to the next. "The first taken by the fishermen at Scarborough is

carefully made a prisoner, and placed on a seat at the stern of the boat.

When they hook a butt (halibut) they immediately give the poor star-fish

its liberty and commit it to its native element; but if their fishery is

unsuccessful it is left to perish, and may eventually enrich the cabinet

of some industrious collector."

To the family of the Asteriæ belongs also the Ling-thorn (_Luidia

fragilissima_), the largest, and one of the most interesting of our

British species. When full grown, it measures two feet across, and would

appear to exceed that size occasionally, judging from fragments. The rays

are from five to seven in number, quite flat, and generally five times

as long as the disk is broad. The colour is brick-red above, varying in

intensity, the under surface being straw-coloured. The wonderful power

which the Luidia possesses, not merely of casting away its arms entire,

but of breaking them voluntarily into little pieces with great rapidity,

approximates it to the brittle-stars, and renders the preservation of a

perfect specimen a very difficult matter.

"The first time I ever took one of these creatures," says Edward Forbes,

"I succeeded in getting it into the boat entire. Never having seen one

before, and quite unconscious of its suicidal powers, I spread it out on

a rowing-bench, the better to admire its form and colours. On attempting

to move it for preservation, to my horror and disappointment I found

only an assemblage of rejected members. My conservative endeavours

were all neutralised by its destructive exertions, and it is now badly

represented in my cabinet by an armless disk and a diskless arm. Next

time I went to dredge on the same spot, determined not to be cheated out

of a specimen in such a way a second time, I brought with me a bucket of

cold fresh water, to which article star-fishes have a great antipathy.

As I expected, a luidia came up in the dredge, a most gorgeous specimen.

As it does not generally break up before it is raised above the surface

of the sea, cautiously and anxiously I sunk my bucket to a level with

the dredge's mouth, and proceeded in the most gentle manner to introduce

luidia to the purer element. Whether the cold air was too much for him,

or the sight of the bucket too terrific, I know not, but in a moment he

proceeded to dissolve his corporation, and at every mesh of the dredge

his fragments were seen escaping. In despair I grasped at the largest,

and brought up the extremity of an arm with its terminating eye, the

spinous eyelid of which opened and closed with something exceedingly like

a wink of derision."

[Illustration: Goniaster.]

The Sea-star might be called a flattened sea-urchin, with radiated

lobes, and the Sea-urchin, a contracted or condensed sea-star, so near

is their relationship. In both we find the same radiating construction,

in which the number five is so conspicuous, and in both also the rows

of suckers, which, starting from a centre, are set into motion by a

similar mechanism, and used for the same purpose. In all the sea-urchins

finally, and in many of the sea-stars, we find the surface of the

body covered with numerous exceedingly minute, two- or three-forked

pincers, that perpetually move from side to side, and open and shut

without intermission. These active little organs, which have been named

_Pedicellariæ_, were formerly supposed to be parasites, working on their

own account, but they are now almost universally recognised as organs

subservient to the nutrition of the animal, and destined to seize the

food floating by, and to convey it to the mouth, one passing it to

the other. Even in their outward appearance, the sea-urchins are not

so very different from the sea-stars as would be imagined on seeing a

Butt-thorn near a globular urchin, for both orders approach each other

by gradations; thus, the Goniasters, with their cushion-shaped disks and

shortened rays, approximate very much in shape to the sea-urchins; and

among the latter we also find a gradual progression from the flattened

to the globular form. Still there are notable differences between the

two classes. Thus in the sea-urchins the digestive organs form a tube

with two openings, while in the true sea-stars they have but one single

orifice. Their mode of life is, however, identical.

[Illustration: Shell of Echinus, or Sea-Urchin.

On the right side covered with spines, on the left the spines removed.]

The Echinidæ move forward by means of the joint action of their suckers

and spines, using the former in the manner of the true star-fishes, and

the latter as the snake-stars. They also make use of the spines, which

move in sockets, to bury themselves in the fine sand, where they find

security against many enemies.

Some species even entomb themselves pholas-like in stone, inhabiting

cavities or depressions in rocks, corresponding to their size, and

evidently formed by themselves. Bennett describes each cavity of the

edible _Echinus lividus_ as circular, agreeing in form with the urchin

within it, and so deep as to embrace more than two-thirds of the bulk of

the inhabitant. It is large enough to admit of the creature's rising a

little, but not of its coming out easily. The echinus adheres so firmly

to this cavity by its suckers, as to be forced from it with extreme

difficulty when alive. On the coasts of the county of Clare thousands

may be seen lodged in the rock, their purple spines and regular forms

presenting a most beautiful appearance on the bottoms of the grey

limestone rock-pools. How the boring is performed has, like many other

secrets, not yet been settled by naturalists. The first perforation is

most likely effected by means of the teeth, and then the rock softened by

some secreted solvent.

[Illustration: Mammillated Sea-Urchin.]

Sea-urchins are found in all seas, but as they are extremely difficult to

preserve, and many of them have such long and delicate spines that it is

almost impossible to procure perfect specimens, probably not one tithe of

their species is known.

On our coasts the common "egg-urchin" affords the poor a somewhat scanty

repast; but, throughout the Mediterranean, its greater size, and also

that of its allies, _Echinus melo_ and _E. sardicus_, render them, when

"in egg," important articles of food. In Sicily these animals are in

season about the full moon of March; there the _E. esculentus_ is still

called the "King of Urchins;" whilst the larger melon-urchin is popularly

considered to be its mother. The size and abundance of these edible

species are among the striking peculiarities of the fish markets of the

Mediterranean sea-board.

[Illustration: Edible Sea-Urchin.]

The calcareous shell of the "sea-urchin" seems, at first sight, to be

composed of one simple crust, but proves, on nearer inspection, to be

a masterpiece of mosaic consisting of several hundred parts, mostly

pentagonal. These are so closely united that their junctions are hardly

visible, but on allowing the shell to macerate for some days in fresh

water, it falls to pieces. This complicated structure is by no means

a mere architectural fancy, a useless exuberance of ornament, but

essentially necessary to the requirements of the animal's growth. A

simple hard crust would not have been capable of distension, whereas

a complicated shell, such as the sea-urchin possesses, can grow in the

same ratio as the internal parts, by continual deposits on the edges of

the individual pieces. On closely examining a living sea-urchin, we find

the whole surface of the shell and spines covered with a delicate skin,

which, in spite of their close connexion, penetrates into the intervals

of the several pieces. This membrane secretes the chalk of which the

shell is composed, and deposits fresh layers on the edges of the plates,

so that in this manner the shell continually widens until the animal has

attained its perfect size. The spines are secreted in the same manner,

and show under the microscope an admirable beauty and regularity of

structure. So bountifully has the great Architect of worlds provided for

the poor insignificant sea-urchin!

[Illustration: Dental Apparatus of the Sea-urchin, viewed from above.]

The dental apparatus of the animal--the so-called lantern of

Aristotle--is another masterpiece in its way. Fancy five triangular

bones or jaws, each provided with a long, projecting, movable tooth. A

complicated muscular system sets the whole machinery going, and enables

the jaws to play up and down, and across, so that a more effective

grinding-mill can scarcely be imagined.

[Illustration:

A. Two sockets with teeth, of Echinus esculentus. B. Single socket

with its tooth viewed on the outside.]

The _Holothuriæ_, or Sea-cucumbers, may be regarded in one light as

soft sea-urchins, and in another as approximating to the Annelides or

worms. Their suckers are similar to those of the true star-fishes and

sea-urchins. Besides progression by means of these organs, they move,

like annelides, by the extension and contraction of their bodies. The

mouth is surrounded by plumose tentacula, the number of which, _when

they are complete_, is always a multiple of five. They all have the power

of changing their shapes in the strangest manner, sometimes elongating

themselves like worms, sometimes contracting the middle of their bodies,

so as to give themselves the shape of an hour-glass, and then again

blowing themselves up with water, so as to be perfectly globular.

[Illustration: Fierasfer.]

The great Sea-cucumber is the largest of all the known European species,

and probably one of the largest _Cucumeriæ_ in the world, measuring when

at rest fully one foot, and capable of extending itself to the length

of three. Under the influence of terror, it dismembers itself in the

strangest manner. Having no arms or legs to throw off, like its relations

the luidia and the brittle-star, it simply disgorges its viscera, and

manages to live without a stomach; no doubt a much greater feat than

if it contrived to live without a head. According to the late Sir

James Dalyell, the lost parts are capable of regeneration, even if the

process of disgorgement went so far as to leave but an empty sac behind.

Considering the facility with which the sea-cucumber separates itself

from its digestive organs, it is the more to be wondered how it tolerates

the presence of a very remarkable parasite, a fish belonging to the genus

_Fierasfer_, and about six inches long. This most impudent and intrusive

comrade enters the mouth of the cucumber, and, as the stomach is too

small for his reception, tears its sides, quartering himself without

ceremony between the viscera and the outer skin. The reason for choosing

this strange abode is as yet an enigma.

[Illustration: Eatable Trepang.]

The _Holothuriæ_, which in our part of the globe are very little noticed,

play a much more important part in the Indian Ocean, where they are

caught by millions, and, under the name of _Trepang_ or _Biche de mer_,

brought to the markets of China and Cochin-China. Hundreds of praos are

annually fitted out in the ports of the Sunda Islands for the gathering

of trepang; and sailing with help of the western monsoon to the

eastern parts of the Indian Archipelago, or along the northern coast of

Australia, return home again by favour of the eastern monsoon. The bays

of the inhospitable treeless shores of tropical New Holland, the abode

of a few half-starved barbarians, are enlivened for a few months by the

presence of the trepang fishers.

"During my excursions round Raffles Bay," says Dumont d'Urville, ("Voyage

to the South Pole,") "I had remarked here and there small heaps of

stones surrounding a circular space. Their use remained a mystery until

the Malayan fishers arrived. Scarce had their praos cast anchor, when

without loss of time they landed large iron kettles, about three feet

in diameter, and placed them on the stone heaps, the purpose of which

at once became clear to me. Close to this extemporised kitchen they

then erected a shed on four bamboo stakes, most likely for the purpose

of drying the holothurias in case of bad weather. Towards evening,

all preliminaries were finished, and the following morning we paid a

visit to the fishermen, who gave us a friendly reception. Each prao had

thirty-seven men on board, and carried six boats, which we found busily

engaged in fishing. Seven or eight Malays, almost entirely naked, were

diving near the ship, to look for trepang at the bottom of the sea. The

skipper alone stood upright, and surveyed their labours with the keen eye

of a master. A burning sun scorched the dripping heads of the divers,

seemingly without incommoding them; no European would have been able

to pursue the work for any length of time. It was about noon, and the

skipper told us this was the best time for fishing, as the higher the

sun, the more distinctly the diver is able to distinguish the trepang

crawling at the bottom. Scarce had they thrown their booty into the boat

when they disappeared again under the water, and as soon as a boat was

sufficiently laden, it was instantly conveyed to the shore, and succeeded

by another.

"The holothuria of Raffles Bay is about six inches long, and two inches

thick. It forms a large cylindrical fleshy mass, almost without any

outward sign of an organ, and as it creeps very slowly along is easily

caught. The essential qualities of a good fisherman are great expertness

in diving, and a sharp eye to distinguish the holothurias from the

similarly coloured sea-bottom.

"The trepang is first thrown into a kettle filled with boiling sea-water.

After a few minutes, it is taken out of its hot-bath and ripped open

with a knife to cleanse it of its intestines. It is then thrown into a

second kettle, where a small quantity of water and the torrefied rind of

a mimosa produce dense vapours. This is done to smoke the trepang for

better preservation. Finally, it is dried in the sun, or in case of bad

weather under the above-mentioned shed. I tasted the trepang, and found

it had some resemblance to lobster. In the China market the Malays sell

it to the dealers for about fifteen rupees the picul of 125 pounds. From

the earliest times, the Malays have possessed the monopoly of this trade

in those parts, and Europeans will never be able to deprive them of

it, as the economy of their outfit and the extreme moderation of their

wants forbid all competition. About four in the afternoon the Malays had

terminated their work. In less than half an hour the kettles and utensils

were brought on board, and before night-fall we saw the praos vanish from

our sight."

The inhabitants of the island of Waigiou, to the north of New Guinea,

prepare the trepang in the Malay manner, and barter it for cotton and

woollen stuffs, which are brought to them by some Chinese junks. "In

every hut," says Lesson, "we found great heaps of this dried leathery

substance, which has no particular taste to recommend it, and is so

highly esteemed by the Chinese for no other reason than because they

ascribe to it,--as to some other gelatinous substances, as agar-agar,

shark-fins, and edible bird's nests,--peculiar invigorating properties,

by means of which their enervated bodies are rendered fit for new

excesses."

The Feejee islanders have the reputation of being the greatest cannibals

and the most perfidious savages of the whole Pacific, yet the trepang

fishery attracts many American and European speculators to that dangerous

archipelago. Captain Wilkes, of the United States Exploring Expedition,

found there a countryman, Captain Eagleston, who had been successful in

more than one of these expeditions, and obligingly communicated to him

all the particulars of his adventurous trade. There are six valuable

sorts of biche de mer, or trepang; the most esteemed is found on the

reefs one or two fathoms deep, where it is caught by diving. The inferior

sorts occur on reefs which are dry, or nearly so, at low water, where

they are picked up by the natives, who also fish the biche de mer on

rocky coral bottoms by the light of the moon or of torches, as they come

forth by night to feed. The most lucrative fisheries are on the northern

side of Viti Levu. They require a large building for drying, with rows

of double staging, on which reeds are placed. Slow fires are kept up by

natives underneath, about fifteen hands being required to do the ordinary

work of a house.

Before beginning, the services of some chief must be secured, who

undertakes the building of the house, and sets his dependants at work to

fish. The usual price is a whale's tooth for a hogshead of the animals

just as they are taken on the reef; but they are also bought with

muskets, powder, balls, vermilion, blue beads, and cotton cloth of the

same colour. When the animals are brought on shore, they are measured

into bins containing about fifty hogsheads, where they remain until next

day. They are then cut along the belly for a length of three or four

inches, taking care not to cut too deep, as this would cause the fish to

spread open, which would diminish its value. They are then thrown into

boilers, two men attending each pot, and relieving each other, so that

the work may go on night and day. No water need be added, as the fish

itself yields moisture enough to prevent burning. After draining on a

platform for about an hour, they are taken to the house and laid four

inches deep upon the lower battens, and afterwards upon the upper ones,

where they remain three or four days. Before being taken on board they

are carefully picked, all damp pieces being removed. They are stowed

in bulk, and sold in Manilla or Canton by the picul, which brings from

fifteen to twenty-five dollars. In this manner Captain Eagleston had

collected in the course of seven months, and at a trifling expense, a

cargo of 1200 piculs, worth about 25,000 dollars. The outfit is small,

but the risk is great, as no insurance can be effected; and it requires

no small activity and enterprise to conduct this trade. A thorough

knowledge of native character is essential to success, and the utmost

vigilance and caution must always be observed to prevent surprise, or

avoid difficulties.

No large canoes should ever be allowed to remain alongside the vessel,

and a chief of high rank should be kept on board as a hostage. That

these precautions are by no means unnecessary, is proved by the frequent

attempts of the savages to cut off small vessels trading on their

coasts. One of the most frequent methods is to dive and lay hold of the

cable; this, when the wind blows fresh to the shore, is cut, in order

that the vessel may drift upon it, or in other cases a rope is attached

to the cable by which the vessel may be dragged ashore. The time chosen

is just before daylight. The moment the vessel touches the land, it is

treated as a prize sent by the gods, and the crew murdered, roasted, and

devoured.

[Illustration: Sea-horse.]

CHAP. XVII.

CŒLENTERATA.

POLYPS AND JELLY-FISHES.

Thread-cells or Urticating

Organs.--Sertulariæ.--Campanulariadæ.--Hydrozoie

Acalephæ.--Medusidæ.--Lucernariadæ.--Calycophoridæ.--The

Velella.--The Portuguese Man-of-war.--Anecdote of a

Prussian Sailor.--Alternating Fixed and Free-swimming

Generations of Hydrozoa.--Actinozoa.--Ctenophora.--Their

Beautiful Construction.--Sea-anemones.--Dead Man's

Toes.--Sea-pens.--Sea-rods.--Red Coral.--Coral Fishery.--Isis

hippuris.--Tropical Lithophytes.--History of the Coral

Islands.--Darwin's Theory of their Formation.--The progress of their

Growth above the level of the Sea.

Despite the low rank they occupy in the hierarchy of animal life, the

Cœlenterata, comprising the numerous families of the Jelly-fishes and

Polyps, play a most important part in the household of the ocean, for the

sea is frequently covered for miles and miles with their incalculable

hosts, and whole archipelagos and continents are fringed with the

calcareous structures they raise from the bottom of the deep.

Their organisation is more simple than that of the preceding classes,

for they have neither the complex intestinal tube of the polyzoa or the

sea-urchins nor the jointed rays or arms of the star-fishes; their whole

digestive apparatus is but a simple sac, and their instincts are reduced

to the mere prehension of the food that the currents bring within reach

of their tentacles, or to the retraction of these organs when exposed to

a hostile attack.

But, simple as they are, they have been provided by Nature with a

comparatively formidable weapon in those remarkable "thread-cells," or

urticating organs, which are so constantly met with in their integuments,

and chiefly in their tentacles.

The thread-cells are composed of a double-walled sac having its open

extremity produced into a short sheath terminating in a long thread.

A number of barbs or hooks are sometimes disposed spirally around the

sheath, the thread itself being often delicately serrated. Under pressure

or irritation the thread-cell suddenly breaks, its fluid escapes, and the

delicate thread is so rapidly projected that the eye is utterly unable to

follow the process. The violent protrusion of this barbed missile, along

with the acrid secretion of the cell, causes many a worm or crustacean

of equal or superior strength, that might have gone forth as victor from

the struggle of life, to succumb to the cœlenterate, and is even in

many cases exceedingly irritating to the human skin. Besides enabling

its possessor to derive his subsistence from animals whose activity, as

compared with his own, might be supposed to have removed them altogether

out of the reach of danger, these stings serve also as admirable weapons

of defence, and many a rapacious crab or annelide that would willingly

have feasted upon a sea-anemone is no doubt repelled by the venomous

properties of its urticating tentacles.

[Illustration: Urticating Organs of Cœlenterata.

_a_, _e_, _f_. Threads and thread-cells of _Caryophyllia Smithii_.

_b._ Thread-cell of _Corynactis Allmani_.

_c._ Peculiar receptacle of _Willsia stellata_, containing thread-cells.

_d._ A single thread-cell of the same.

_g._ Thread-cell of _Actinia crassicornis_.--(All magnified.)

]

The Cœlenterata have been subdivided into two great classes: the

Hydrozoa, in which the wall of the digestive sac is not separated from

that of the cavity of the body, and the Actinozoa, in which the stomach

forms a distinct bag separated from the wall of the cavity of the body by

an intervening space, subdivided into chambers by a series of vertical

partitions. Each of these two classes comprises a number of families of

various forms and habits of life. Thus among the Hydrozoa, with whom I

begin my brief survey of cœlenterate life, some are of a compound nature

(Sertularidæ, &c.), and, having once settled, remain permanently attached

to the site of their future existence; while others (Rhizostomidæ, &c.)

continue freely to roam through the water, and others again appear in

the various stages of their development either as sessile polyps or as

free-swimming Medusæ.

The sertularian tribes are remarkable for the elegance of their forms,

resembling feathers more or less stiff and angular, more or less flexible

and plumose. Their bleached skeletons are among the commonest objects

thrown out by the waves, and so plant-like is their appearance and manner

of growth that, like the Flustræ, they might easily be mistaken for

sea-weeds.

[Illustration: Sertularia tricuspidata.

_a._ Skeleton (natural size).

_b._ Portion of the same, highly magnified.

_κ._ _Cœnosarc_, or common trunk.

_π′._ _Hydrotheca_, or protective envelope of individual polyp.

_ρ′._ _Gonoblastidium_, or reproductive germ or body.

]

Originally produced from a single ovulum, every species, by the evolution

of a succession of buds, after an order peculiar to each, grows up to a

populous colony, and simultaneously with its growth the fibres by which

it is rooted extend, and at uncertain intervals give existence to similar

bodies, whence new polypiferous shoots take their origin, for these root

fibres are full of the same medullary substance with the rest of the

body. Thus the graceful sea-fir (_Sertularia cupressina_), the largest

of our native species, may attain a height of two or three feet, and bear

on its branches no less than 100,000 distinct microscopical polypi, each

with its own crown of tentacles, and each of these armed with numerous

thread-cells, as formidable in their way as the crustacean's claw or

the annelide's embrace. But though each polyp has a certain share of

independence yet its body is continuous with the more fluid pulp that

fills the branches and stem of the common trunk, and by this means all

the polyps of it are connected together by a living thread, and made to

constitute a family whose workings are all regulated by one harmonious

instinct. Each of these plant-like structures may therefore be considered

as one animal furnished with a multitude of armed heads and mouths, and

in all the other compound cœlenterates we find a similar organisation.

All the soft parts of a sertularian polypary are enclosed in a horny

sheath (_hydrosoma_) which develops peculiar cup-shaped processes

(_hydrothecæ_) for the protection of each individual polyp, and capsules

for the reproductive bodies (_gonoblastidia_) in which the ova are

produced. The various modifications of form and structure of the polyps,

of their hydrothecæ and gonoblastidia, give rise to a number of families,

genera, and species. Thus in the Sertulariæ the polypites are sessile,

biserial, alternate, or paired; sessile and uniserial in the Plumulariæ,

and stalked in the Campanulariadæ.

[Illustration:

_a._ _Laomedea neglecta_, natural size.

_b._ Portion of the same, magnified.

_c._ Reproductive body of _Campanularia volubilis_.

_e._ Reproductive body of _C. syringa_.

]

The free-swimming Jelly-fishes, or Acalephæ, as they have been named by

Aristotle on account of the stinging properties due to their urticating

cells, are likewise among the commonest objects left upon our shores

by the retreating tide. When stranded, they appear like gelatinous

masses, disgusting to the sight; but these shapeless objects were

beautiful while they moved along in their own element, and their simple

organisation shows no less the masterhand of the Creator than the complex

structure of the higher stages of animal existence. With the exception

of the Ctenophora, they all belong to the hydrozoic class, and from the

great diversity of their structure have been ranged under four orders,

Medusidæ, Lucernaridæ, Calycophoridæ, and Physophoridæ.

[Illustration:

_a._ Medusid seen in profile.

_b._ The same viewed from below.

_c._ Its polypite.

_d._ Part of its marginal canal, and other structures in

connection therewith.

ν. Disk or swimming organ.

π. Polypite.

ψ. Veil.

τ. Tentacle.

χ. Radiating canal.

χ′. Marginal canal.

ω. Reproductive organ.

ο′. Coloured spot.

ο″. Marginal vesicle.

]

The Medusidæ are distinguished by their globular or bell-shaped disc,

which by its alternate contractions and expansions forces them forward

through the water. By contracting the whole or only part of its disc,

the medusa has it in its power to direct its movements, and while thus

swimming along with the convex side of the disc directed forwards, and

its oral lobes and tentacles following behind like "streamers long and

gay," it may well rank among the most elegant children of the sea.

From the roof of the disc a single polypite is suspended, whose mouth,

generally produced into four lobes, though in some forms it is much

more divided, passes into the central cavity (stomach) of the swimming

organ, from which canals (either four in number, or multiples of four)

radiate to join a circular vessel surrounding the margin of the bell.

A shelf-like membrane or veil, extending around the margin, and highly

contractile, assists locomotion by narrowing more or less the aperture

of the bell, and thus concentrating its efforts upon a narrower space.

More or less numerous tentacles generally depend from the margin, and

around it are disposed two kinds of remarkable bodies--"vesicles" and

"pigment spots," or "eye-specks"--which are supposed to be able to

communicate the impressions of light and sound. This complexity of

organisation in creatures which Réaumur contemptuously styled mere lumps

of animated jelly is all the more wonderful when we consider that they

consist almost entirely of water, and shrink to a mere nothing when

abandoned by their vital power. Thus of a medusa originally weighing many

pounds but few traces remain after death; the ground is covered with a

light varnish; all the rest has been absorbed by the thirsty sands.

[Illustration: Various forms of Medusidæ.

_a._ _Aequorea formosa_, seen in profile.

_b._ The same, viewed from above.

_c._ Upper view of _Willsia stellata_.

_d._ _Slabberia conica._

_e._ Portion of the marginal canal of _Tiaropsis Pattersonii_.

_f._ Polypite of _Bougainvillea dinema_.

_g._ Part of its marginal canal.

_h._ _Steenstrupia Owenii._ (_a_, _b_, and _d_ are about the natural

size; the others are magnified.)

]

The oceanic or free-swimming forms of the Lucernaridæ resemble the

Medusidæ by their bell-shaped umbrella, but differ from them by their

internal structure, by the absence of a marginal veil, by the nature of

their canal system and marginal bodies, and by their mode of development.

The radiating canals, never less than eight in number, send off numerous

branches, which form a very intricate network, and the vesicles and

pigment-spots, here united into a single organ, termed the lithocyst, are

each protected externally by a sort of hood, whence these jelly-fishes

have been named "Stegonophthalmia," or "covered-eyed," by Forbes, to

distinguish them from the naked-eyed "Gymnophthalmia," or Medusidæ. The

Pelagidæ (Chrysaora), which form one of the divisions of this group,

are simple, and have their margin surrounded with tentacles like the

Medusidæ, while the Rhizostomidæ have no marginal tentacles, and consist

of numerous polyps studding the trunks of a dependent tree. These animals

have consequently no central mouth, but hundreds of little mouths all

active for the welfare of the community.

[Illustration: Oceanic forms of Lucernaridæ.

_a._ _Rhizostoma pulmo._

_b._ _Chrysaora hysoscella._

_c._ Its lithocyst.--(All reduced.)

]

The sessile Lucernaridæ differ from the other members of the order by the

narrow disc or stalk which serves to fix their body when at rest. Their

quadrangular mouth is in the centre of the umbrella expansion, and round

the margin of the cup arise a number of short tentacles, disposed in

eight or nine tufts in Lucernaria, and forming one continuous series in

Carduella.

[Illustration: Lucernalia auricula. (Natural size.)]

Though generally preferring to lie at anchor, the Lucernaridæ are able

to detach themselves, and to swim in an inverted position by the slowly

repeated movements of their cup-like umbrella. When in a state of

expansion, few marine creatures exceed them in beauty and singularity

of form; when contracted, they are shapeless, and easily overlooked.

"Their mode of progression," says Mr. Couch, "differs under different

circumstances. If intending to move to any great distance, they do so by

loosening their attachments, and then, by various and active contortions,

they waft themselves away till they meet with any obstruction, where they

rest; and if the situation suits them, they fix themselves; if not, they

move on in the same manner to some other spot. If the change be only for

a short distance, as from one part of a leaf to another, they bend their

campanulate rims, and bring the tentacula in contact with the jaws, and

by them adhere to it. The foot-stalk is then loosened and thrown forward

and twirled about till it meets with a place to suit it; it is then

fixed, and the tentacula are loosened, and in this way they move from one

spot to another. Sometimes they advance like the Actiniæ, by a gliding

motion of the stalk. In taking their prey, they remain fixed with their

tentacula expanded, and if any minute substance comes in contact with any

of the tufts, that tuft contracts, and is turned to the mouth, while the

others remain expanded watching for prey."

The Calycophoridæ are distinguished by the cup-shaped swimming organs,

which form the most prominent part of their body. Generally transparent

like glass, their course upon distant inspection is only revealed by the

bright tints of some of their appendages. In Diphyes, the type of the

group, the two cups (ν, ν′′) fit into each other so as to form a

more or less perfect close canal. The common stem of the numerous polyp

colony freely glides up and down the chamber thus formed, into which it

can be completely retracted, and along its sides are placed the several

appendages of the compound creature, consisting chiefly of polypites

(π), tentacles, and organs of reproduction. Large specimens of

Diphyes attain, when fully extended, a length of several inches, the stem

giving support to at least fifty different polypites. The other genera

of the order exhibit a great variety in the form and arrangement of

their various parts; thus, in Vogtia, each of the swimming organs (ν)

is produced into five points, of which the three upper are much longer

and stronger than the two lower. The individual polyps (π), large in

size, but few in number, are congregated immediately under the swimming

apparatus, and are provided with long and formidable tentacula.

[Illustration: _a._ Diphyes appendiculata.]

[Illustration: _b._ Vogtia pentacantha. (Natural size.)]

In the Physophoridæ the basal end of the common polyp stem is modified

so as to form a float or aëriform sac, which is, however, extremely

different in shape, structure, and size in the various families. In

the Velellæ, the float, whose under surface is studded, besides one

larger central polypite, with numerous small nutritive, reproductive,

and tentacular bodies, forms a horizontal disc traversed by a diagonal

triangular crest, and divided into numerous hollow chambers. Thus

equipped, the semi-transparent velella, beautifully tinged with

ultramarine, sails on the surface of the warmer seas, but the currents

of the Gulf Stream, and the westerly winds, frequently drift it to the

coast of Ireland, where it is often found on the beach, entangled in

masses of sea-weed. Of the vast numbers in which it sometimes occurs,

Herr von Kittlitz relates an interesting instance in his "Travels to

Russian America and Micronesia." "Having passed 30° N. lat. in the

Pacific, the sea was suddenly found covered with myriads of Velellæ, of a

size somewhat greater than the Atlantic species." Two days long the ship

sailed through these floating masses, when suddenly the scene changed,

and large clusters of barnacles appeared, which, having no doubt devoured

the soft parts of the Velellæ, now invested their horny skeletons. As

the ship advanced, the number of the barnacle clusters augmented, which,

to judge from the various sizes of the individuals, must have taken

some time for their formation, and were apparently destined to increase

until the final destruction of the Velellæ hosts, into which, from their

greater weight, they were continually drifting deeper and deeper by the

action of the currents. Again two or three days elapsed, and as the

surface of the sea occupied by both species of animals extended at the

least over four degrees of latitude, a faint idea may be formed of their

numbers. Shoals of dolphins and sperm-whales were busy exterminating

the barnacles, as these had devoured the Velellæ. The whole scene was

an example on the grandest scale of the destruction and regeneration

perpetually going on in the wastes of the ocean.

[Illustration:

_a_. _Velella spirans_, somewhat enlarged.

_b._ One of its smaller polypites, much magnified.

ν. Crest.

λ. Liver.

ο. Mouth of polypite.

δ. Its digestive cavity.

φ′. Rounded elevations, containing thread-cells.

ρ. Medusiform zoöids.

]

[Illustration: Physalia caravella.--(Considerably reduced.)

α. Pneumatophore, or float-bladder.

π. Polypites.

τ. Tentacles.

]

The Physaliæ, which far surpass the Velellæ in size and beauty, are

also inhabitants of the warmer seas, where the _Physalia caravella_,

or "Portuguese man-of-war," is the mariner's admiration. On a large

float-bladder eight or nine inches long and three inches broad, whose

transparent crystal shines in every shade of purple and azure, rises a

vertical comb, the upper border of which sparkles with fiery red. This

beautiful float has a small opening at either end, and strong muscular

walls, so that by their contraction its cavity can be considerably

diminished. And thus partly by the escape of air forced out through the

openings, and partly by the compression of what remains, the specific

gravity is so much altered as to admit of the animal's sinking into

the deep when danger threatens. Numerous polyps proceed from the lower

surface, accompanied by tentacles having a sac-like extension at their

base, and hanging down in beautifully blue and violet coloured locks

or streamers. When fully extended, these tentacles form fishing lines

fifteen or sixteen feet long, which, as their thread-cells are uncommonly

large, at once paralyse the resistance of the fish or cephalopod they

meet with. Then rolling together, they convey the senseless prey to the

numerous mouths of the compound animal, which, sucking like leeches, pump

out its nutritious juices. In this manner the greedy physalia devours

many a bonito or flying-fish of a size far superior to its own, and such

is the corrosive power of its tentacles that even man is punished with

excruciating pains when heedlessly or ignorantly he comes within their

reach. "One day," says Dutertre in his "History of the Antilles," "as

I was sailing in a small boat, I saw a physalia, and as I was anxious

to examine it more closely, I tried to get hold of it. But scarcely

had I stretched out my hand when it was suddenly enveloped by a net of

tentacles, and after the first impression of cold (for the animal has a

cold touch) it seemed as if my arm had been plunged up to the shoulder in

a caldron of boiling oil, so that I screamed with pain." In his journey

round the world, Dr. Meyen also relates the case of a sailor who jumped

overboard to catch a physalia. But scarce had he come within reach of its

tentacles when the excruciating pain almost deprived him of sensation,

and he was with great difficulty hauled out of the water. A severe fever

was the consequence, and his life was for some time despaired of.

Several of the Physophoridæ are provided, besides the float, with

swimming-bells (_nectocalyces_) and peculiar appendages or bracteæ

(_hydrophyllia_), which, overlapping the polypites, serve for their

protection. The graceful _Athorybia rosacea_ possesses from twenty to

forty of these organs inserted in two or three circlets immediately below

the pneumatocyst, and above a much smaller number of polypites.

It has the power of alternately raising and depressing them so as to

render them agents of propulsion.

The Physophoræ have no hydrophyllia, but their swimming-bells are

considerably developed, and serve as powerful instruments of locomotion.

They are also provided with certain processes termed "hydrocysts," which

some observers appear disposed to regard as organs of touch. Such are but

a few of the numerous genera of the Physophoridæ.

[Illustration: Physophora Philippii.

α. Pneumatophore.

ν. Swimming-bells.

φ. Hydrocysts.

π. Polypites.

τ. Tentacles.

]

Of the jelly-fishes in general it may be remarked that, though they are

denizens of the frigid as well as of the temperate and tropical seas,

their beauty increases on advancing towards the equator, for while the

Medusæ in our latitudes are generally dull and obscure, those of the

torrid zone appear in all the splendour of the azure, golden-yellow, or

ruby-red tints which distinguish the birds and fishes of those sunny

regions. They are indeed of no immediate use to man, but their indirect

services are not to be despised. They partly nourish the colossal whale,

and thus, converted into oil, attract thousands of hardy seamen to the

icy seas; numberless Crustacea and molluscs also live upon their hosts,

and are in their turn devoured by the mighty herring shoals, whose

capture gives employment and wealth to whole nations of fishermen.

[Illustration: Development of Chrysaora hysoscella.

_a._ Ova with gelatinous investment.

_b_ and _c_. Free ova.

_d._ Young Hydratuba developed therefrom.

_e._ The same with eight tentacles.

_f._ Hydratuba in its ordinary condition.

_g_, _h_. More advanced forms, with constrictions.

_i._ A specimen undergoing fission, in which the tentacles are seen

to arise from below the constricted portion, while its upper

segments separate and become free-swimming zoöids (_k_).

]

Armed with that wonderful instrument, the microscope, naturalists have

been taught to disunite in many cases animals which from their external

resemblance were formerly supposed to belong to the same class or family;

and to join others to all appearances extremely dissimilar. Thus the

Bryozoa have been detached from the polyps, in spite of their similitude

of growth, while the roaming and fixed Hydrozoa have been found in many

cases to be but alternating generations or various phases of development

of the same animal. Take, for instance, _Chrysaora hysoscella_ (see

preceding figure, page 351), one of our commonest jelly-fishes. The ova

this free-swimming creature produces might naturally be supposed to

develop themselves into equally free-swimming Chrysaoræ; but instead

of this they soon become attached, and grow into a colony of sessile

Hydratubæ, as, at this stage of their career, they have been termed.

For years they may thus continue, but then the evolutions shown in the

annexed illustration take place until free-swimming zoöids are detached,

which eventually become similar to the huge Chrysaora, from one of whose

ova the primitive hydratube was produced.

[Illustration: Various forms of Coryniadæ.

_a_ and _b_. _Vorticlava humilis._

_c._ Four polypites of _Hydractinia echinata_, growing on

a piece of shell.

_d._ Portion of _Syncoryne Sarsii_, with medusiform zoöids (ρ),

budding from between the tentacles (τ) of the polypite (ο).

--(All, except _a_, magnified.)

]

In a similar manner the Coryniadæ, a family of hydrozoic polyps, which,

unpossessed of the firm investment of the sertularians, are frequently

found decking sea-weeds and stones with dense arborescent structures,

give birth to detached medusiform zoöids. On the other hand, many medusid

forms produce organisms directly resembling their parents, and many fixed

Hydrozoa, such as the Sertularidæ, do not give birth to free-swimming

medusoids, but to ciliated gemmules, which, escaping from the capsules

in which they had been formed, soon evolve themselves into true polyps.

A great part of this "strange eventful history" is still enveloped

in darkness, as the life of comparatively but few Hydrozoa has been

thoroughly investigated; so much is certain that future observations will

bring many new interesting relationships to light, and add new links to

the chain which binds together the various members of the hydrozoic class.

Although the Ctenophora, thus named from the ciliated bands which

constitute so obvious a feature in their physiognomy, closely resemble

the Medusæ by their gelatinous consistence and their mode of life,

yet a more complex organisation assigns them the highest rank among

the Actinozoa, and approximates them to the sea-anemones. The elegant

_Pleurobrachia pileus_, which in the summer so often appears on our

coasts in countless multitudes, is the species that has been longest

known. The melon-shaped body, from half an inch to nearly an inch

in length, is clear as crystal, and divided by eight longitudinal

equidistant ribs into eight equally large segments or fields. These

ribs are covered with numberless flat paddles or ciliæ, placed one

above another, and obeying the will of the animal. When it wishes to

swim backwards or forwards, it sets all its paddles in motion, whose

united power drives the living crystal rapidly and gracefully through

the water; and when it wishes to turn, it merely stops their movements

on one side. In sunlight, the ribs of the pleurobrachia sparkle with all

the colours of the rainbow; in darkness they emit a beautiful cerulean

phosphorescence.

The prehensile apparatus of the elegant little creature is no less

beautifully organised than its locomotive mechanism. It consists of two

long tentacles emerging from the under part of the body, and capable

of so wonderful a contraction as entirely to disappear within its

cavity, where they are lodged in tubular sheaths. On one side they are

provided at regular intervals with shorter and much thinner filaments,

which roll together spirally when the chief tentacle contracts, and

expand when it is stretched forth. On the secondary branches themselves

still more minute threads are said to have been observed. Words are

unable to express the beauty which the entire apparatus presents in the

living animal, or the marvellous ease with which it can be alternately

contracted, extended, and bent at an infinite variety of angles.

Most of the Ctenophora are spheroidal or ovate, but in Cestum elongation

takes place to an extraordinary extent, at right angles to the direction

of the digestive track, a flat ribbon-shaped body, three or four feet in

length, being the result. The Callianiræ are remarkable for having their

ciliated ribs elevated on prominent wing-like appendages, and the Beroës,

which have no tentacles, receive their nourishment through a widely

gaping mouth, whose size makes them amends for the deficiency of other

prehensile organs. Such are but a few of the varieties exhibited by the

beautiful and interesting Ctenophora.

In habit they resemble the oceanic Hydrozoa, like them swimming near

the surface in calm weather, and again descending on the approach of a

squall. Like them also, their delicate structures rapidly disappear when

removed from the sea-water and exposed to the rays of the sun, an almost

imperceptible film remaining the only trace of what was erewhile an

active and beautiful organism. Yet in spite of their aqueous consistence

the Ctenophora are very voracious, feeding on a number of floating marine

animals, among which their own kindred seem especially to be preferred.

The prey once swallowed is assimilated with a rapidity which to some may

seem strange when the simple structure of the digestive apparatus is

considered.

[Illustration: Various forms of Ctenophora.

_a. Cestram Veneris._ _b. Eurhamphæa vexilligera._ _c. Beroë

rufescens._ _d. Callianira triploptera._ _e. Pleurobrachia pileus._

(_a_ is considerably reduced; _b_ slightly so; _c_ and _e_ are about

the natural size; the size of _d_ is uncertain.)

]

The land has its flowers; they bloom in our gardens, they adorn our

meadows, they perfume the skirts of the forest, they brave the winds that

blow round the high mountain peaks, they conceal themselves in the clefts

of rocks, or spring forth out of ruins; wherever a plant can find room

there Flora appears with her lovely gifts.

But the ocean also has its large radiate anemones, whose lustrous petals,

still more wonderful than those of the land, for they are endowed with

animal life, form the chief ornament of the crystal tide-pools, or of the

sheltered basins of our rock-bound shores.

More than twenty species of these marine flowers, many of them displaying

a gorgeous wreath of richly coloured tentacles, are denizens of the

British waters; but the finest and largest are found along the margin of

the equatorial ocean, where they occasionally measure a foot in diameter.

Their tints are as various as the arrangement of their prehensile crown;

fiery red and apple-green, yellow and white as driven snow. Sometimes the

tentacles form a gorgon's head of long thick worms, clothed in satin and

velvet, and sometimes a thicket of delicate filaments.

Nothing seems more inoffensive than a sea-anemone expanding its disc in

the tranquil waters, but woe to the wandering annelide, to the shrimp, or

whelk, or nimble entomostracon, that comes within reach of its urticating

tentacles, for, plunged into a fatal lethargy, it is soon hurried to

the gaping mouth of its voracious enemy, ever ready to engulf it in a

living tomb. The morsel thus swallowed is retained in the stomach for

ten or twelve hours, when the undigested remains are regurgitated,

enveloped in a glairy fluid, not unlike the white of an egg. The size of

the prey is frequently in unseemly disproportion to the preyer, being

often equal in bulk to itself. Thus Dr. Johnstone mentions a specimen of

_Actinia crassicornis_, that might have been originally two inches in

diameter, and that had somehow contrived to swallow a scallop-valve of

the size of an ordinary saucer. The shell fixed within the stomach was

so placed as to divide it completely into two halves, so that the body,

stretched tensely over, had become thin and flattened like a pancake.

All communication between the inferior portion of the stomach and the

mouth was of course prevented; yet instead of emaciating and dying of an

atrophy, the animal had availed itself of what undoubtedly had been a

very untoward accident to increase its enjoyments and chances of double

fare. A new mouth, furnished with two rows of numerous tentacula, was

opened upon what had been the base, and led to the under stomach; the

individual had indeed become a sort of Siamese twin, but with greater

intimacy and extent in its unions.

From this instance we may naturally infer that the Actiniæ are no mean

adepts in the art of accommodating themselves to circumstances. They may

be kept without food for upwards of a year; they may be immersed in water

hot enough to blister their skins, or exposed to the frost, or placed

within the exhausted receiver of the air-pump, and their hardy vital

principle will triumph over all these ordeals. Their reproductive powers

are truly astonishing. Cut off their tentacles, and new ones sprout

forth; repeat the operation, and they germinate again. Divide their

bodies transversely or perpendicularly through the middle, and each half

will develop itself into a more or less perfect individual.

But these apparently indestructible creatures die almost instantly when

plunged into fresh water, which is for them, or for so many other marine

animals, a poison no less fatal than prussic acid to man.

Though generally firmly attached by means of a glutinous secretion from

their enlarged base to rocks, shells, and other extraneous bodies,

the sea-anemones can leave their hold, and remove to another station,

whensoever it pleases them, either by gliding along with a slow and

almost inperceptible movement or by reversing the body and using the

tentacula as feet; or, lastly, inflating the body with water so as to

diminish its specific weight, they detach themselves, and are driven to a

distance by the random motion of the waves. They are extremely sensible

not only to external irritations--the slightest touch causing them to

shrink into a shrivelled shapeless mass--but also of atmospherical

changes. They hide their crown under a glare of light; but in a calm

and unclouded sky expand and disclose every beauty, while they remain

contracted and veiled in cloudy or stormy weather. The Abbé Dicquemare

has even found, from several experiments, that they foretell changes of

the weather as certainly as the barometer. When they remain naturally

closed there is reason to fear a storm, high wind, and a troubled sea;

but a fair and calm season is to be anticipated when they lie relaxed

with expanded tentacula. The ova of the Actiniæ are detained for some

time after their separation in the interseptal spaces, or even in the

stomach, and there hatched, as it were, into their lasting form. On

emerging into the open ocean, they already resemble their full-grown

relatives, the only difference consisting in a smaller number of

tentacles and septa. The sea-anemones were consequently supposed to be

viviparous, an error which more accurate observations have fully refuted.

[Illustration: Alcyonidium elegans.

_a._ Branch to which the polypary is fixed.

_b._ Foot.

_c._ Trunk.

_d._ Polyp-bearing branches.

_e._ Polyps contracted within the foot.

]

Both the Ctenophora and the Sea-Anemones are single or solitary, but the

vast majority of the Actinozoa consist of aggregated animals attached to

one another by lateral appendages, or by their posterior extremity, and

participating in a common life, while at the same time each member of the

family enjoys its independent and individual existence. These compound

polyps are all either _Alcyonarians_, in which each polyp is furnished

with eight pinnately fringed tentacles, or _Zoantharians_, in which the

tentacula are simple or variously modified, and generally disposed in

multiples of five or six. The Alcyonarians are again subdivided into the

four families of the Alcyonidæ, the Pennatulidæ, the Gorgonidæ, and the

Tubiporidæ.

The Alcyonidæ vary much in form, being either lobed, branched, rounded,

or existing in a shapeless mass or crust, while the interior substance

is of a spongy or cork-like nature, surrounded by tubular rays enclosed

in a sort of tough fleshy membrane. The _Alcyonium digitatum_ is one of

our most common marine productions, so that on many parts of the coast

scarce a shell or stone can be dredged from the deep that does not

support one or more specimens. As it lies on the shore, it certainly

offers few inducements from its beauty to recommend it to further

notice, and seems fully to warrant the more expressive than elegant

names of "cow's paps," "dead man's toes," or "dead man's hands," which

the fishermen have conferred on it. On putting one of these shapeless

masses into a glass of sea-water, however, and allowing it to remain

for a little time undisturbed, its real nature becomes apparent, and a

series of most interesting phenomena present themselves. The dull orange

mass, which was at first opaque and of a dense texture, slowly swells and

becomes more diaphanous, apparently by the absorption of the surrounding

water into its substance, until, having attained its full dimensions,

numerous dimples appear, studding its entire surface, each of which, as

it gradually expands, reveals itself to be a cell, the residence of a

polyp, which, gradually protruding itself, pushes out a cylindrical body,

clear as crystal, fluted like a column, and terminated by a coronet of

eight delicately fringed tentacula. The unsightly aspect of the trunk,

which reminded us of cadaverous fingers or toes, is now forgotten, just

as we forget the uncouth branches of a cactus when we see it clothed with

its gorgeous flowers. All the polyp-cells are connected by a complicated

system of inosculating canals, bound together by a fibrous network,

and lying imbedded in a transparent jelly, which forms the fleshy part

of the compound animal. The eggs are lodged in the tubes, and at length

discharged through the mouth.

The Sea-Pens, or Pennatulæ, are remarkable from the circumstance that,

although they possess an internal calcareous support, they are not

permanently attached to foreign bodies. The lower portion of the stem,

which strikingly resembles the barrel of a quill, is naked, and, when

found in the bays upon our coast, is generally stuck into the mud at

the bottom like a pen into an inkstand, whilst the upper two thirds of

the stem are feathered with long closely set pinnæ, comparable to the

barbs of a quill, from the margin of which are protruded the rows of

polyps which minister to the support of the common body of the compound

animal. The purple-red _Pennatula phosphorea_, which is found in great

plenty sticking to the baits on the fishermen's lines, especially when

they use muscles to bait their hooks, is one of the most singular

and elegant of the British sea-pens. Some authors believe that it

is capable of using its fin-like arms like oars, but observations

are wanting in corroboration. The pale orange fawn _Virgularia

mirabilis_, an allied species, has a more elongated slender form than

the pennatula. Its rod-like body, from six to ten inches long, is

furnished with short fin-like lobes of a crescent shape, which approach

in pairs, but are not strictly opposite; they are about the eighth of

an inch asunder, and are furnished along the margins with a row of

urn-shaped polyp-cells. These very delicate and brittle animals seem

to be confined to a small circumscribed part of the coast, which has a

considerable depth and a muddy bottom, and the fishermen accustomed to

dredge at that place believe from the cleanness of the Virgulariæ, when

brought to the surface, that they stand erect at the bottom with one

end fixed in the mud or clay.

[Illustration: Grey Sea-Pen.]

[Illustration: Virgularia mirabilis.]

The Gorgonidæ (Gorgonia, Primnoa, Corallium, Isis, Mopsea) mainly differ

from the Alcyonidæ in having an erect and branching stem, firmly rooted

by its expanded base. A soft and fleshy crust, studded with numerous

polyps, envelops a solid horny or calcareous axis, which serves as a

support to the arborescent structure, and enables it to rise to a height

of several feet, or even, if we are to credit the Norway fishermen, to

rival our forest-trees in magnitude. This they conclude to be the case

from their nets being sometimes entangled on the trunk or stem of the

_Primnoa lepadifera_, as this large species of gorgon is called, when the

united strength of several men is unable to free the nets. "They have

even assured me," says Sir A. Capell de Brooke, "that the corals grow

to the height of fifty or sixty feet, as they judge from the following

circumstance, which seems clear and simple. The lines for the red-fish,

which is found in the greatest plenty where the primnoa grows, are set in

very deep water at the distance of about six feet from the bottom, and

in the parts where it is flat and level, which they can tell from their

soundings. On drawing up the lines at the distance of forty, fifty, or

sixty feet, and sometimes even more from the bottom, they get entangled

with some of the upper parts or branches of the gorgon, which are thus

torn off, and hence they reasonably conclude that the animal rises to

this height."

The Gorgonidæ either branch away irregularly like shrubs, or else their

branches inosculate and form a kind of net or fan, as in the _Flabellum

Veneris_, a beautiful Indian species, which some naturalist of more than

usual fancy has appropriated to the use of Venus.

Four British species of Gorgonia are recorded. _G. verrucosa_, the

commonest of these, abounds in deep water along the whole of the south

coast of England. It is more than twelve inches in height, and fifteen or

seventeen in breadth, and expands laterally in numerous cylindrical and

warty branches. It is somewhat fan-shaped, but does not form a continuous

network. Its coral has a dense black axis, with a snow-white pith in the

centre, and is covered, while living, with a flesh-coloured crust. The

flexible corneous stem of the Gorgonias enables them to bend beneath the

passing current, and thus prevents their long and slender ramifications

from breaking, while the hard calcareous branches of the valuable red

coral (_Corallium nobile_) are sufficiently short and strong to resist

the violence of the sea. This beautiful marine production, though also

occurring in the Ethiopic Ocean and about Cape Negro, is chiefly found in

the Mediterranean, on the shores of Provence, about the isles of Majorca

and Minorca, on the south of Sicily, and on the coast of Africa. It grows

on rocky bottoms, and frequently in an inverted position, or downwards

from the under surface of stones, generally at a depth of several hundred

feet.

[Illustration: Red Coral.

Gorgonia nobilis. (A small detached portion magnified.)]

When alive, the soft rind which invests the valuable central stony axis

is studded with snow-white polyps. The fishery is still carried on in

the same way as it was described by Marsigli 150 years ago. The net is

composed of two strong rafters of wood tied crosswise, with leads fixed

to them; to these they fasten a quantity of hemp twisted loosely round

and intermingled with some loose netting. This apparatus is let down, and

while the boat is sailing or being rowed along, alternately raised and

dropped so as to sweep a certain extent of the bottom and to entangle

the corals in its coarse meshes. The labour, as may be imagined, is very

great; frequently, after a long toil, the net is brought up empty, or

filled only with other marine productions, which, however interesting

they may be to the naturalist, are perfectly worthless in the eyes of the

coral-fisher; and not seldom immense exertions are required to loosen it

from the rocks, among which it has got entangled.

The chief seat of the coral-fishery is at present along the coasts

of Algeria and Tunis, where it is almost exclusively carried on by

the Italians, who fit out more than 400 small ships, or "corallines,"

of from five to sixteen tons, for this purpose. In spring this fleet

of nut-shells leaves the ports of Torre del Greco, Sicily, Sardinia,

and Genoa, and proceeds to its various points of destination, where

it remains until the autumnal gales compel the fragile "corallines"

to retire. Every month or fortnight the products of the fishery are

delivered up to agents in Bona or La Calle, under whose direction the

corals are sorted, packed in cases, and sent to Naples, Leghorn, or

Genoa, where they are cut, polished, and manufactured into necklaces and

other ornaments or trinkets. About 4,000 sailors are employed in the

fishery, each man receiving an average pay of 380 franks for the season,

which he almost entirely brings home with him, his trifling expenses on

land being generally defrayed by the small pieces of coral he manages

to conceal from the sharp eye of the "padrone." The average quantity of

corals fished by each "coralline" amounts to about six hundredweight, and

the total value of the fishery to more than 200,000_l._, without taking

into account the produce of the fisheries at Stromboli, in the Straits of

Messina, and other parts of the Italian coast.

The manufactured articles sell of course for a much higher price, so

that the "red coral" is a by no means inconsiderable article of trade.

Great quantities are exported to India, and in Leghorn and Genoa several

large manufactories work exclusively for that distant market, where the

blood-red corals, whose colour harmonises with the dark complexion of the

native ladies, are particularly in demand, while those of a roseate hue

are preferred in Europe.

The fishermen have a strange belief that the corals are by nature soft,

but immediately turn into stone from terror when entangled by the net.

There is also a legendary tale of an enchanted coral-tree, large and

powerful as an oak, which is said to grow in a deep grotto at the foot of

Mont Alban, on the Ligurian coast. It extends its arms when no danger is

nigh, but immediately withdraws them, like a cuttle-fish, at the approach

of an insidious enemy. This superstition is so firmly rooted that, while

Professor Vogt was at Villafranca in 1865, a "coralline" arrived from

Torre del Greco for the purpose of fishing for this imaginary prey.

The "padrone" swore he would not leave the neighbourhood before he had

secured his prize, hoping to enrich himself with the spoils, but doomed,

no doubt, to a grievous disappointment, and a considerable loss, on a

coast where but few ordinary corals are found.

[Illustration: Isis hippuris.]

In the elegant _Isis hippuris_, which grows in the Indian Ocean, and is

frequently found in cabinets of natural history, the horny and calcareous

matter of the axis is disposed in alternate joints, so as to unite

flexibility with firmness. A similar structure of alternately disposed

calcareous and horny segments occurs in Mopsea. In Isis branches are

developed from the calcareous, in Mopsea from the horny segments of the

axis.

[Illustration: Tubipora Musica.]

The Tubiporidæ are confined to the narrow limits of a single genus

containing but few species. Here the polypary is composed of distinct

calcareous tubes rising from a fleshy or membranaceous basis, and

arranged in successive stages. These tubes are separated from each

other by considerable intervals, but mutually support each other by the

interposition of external horizontal plates, formed of the same dense

substance as themselves, by which they are united together, so that

a mass of these tubes exhibits an arrangement something like that of

the pipes in an organ, whence the beautiful Indian species, _Tubipora

musica_, has derived its name. From the upper ends of the tubes the

polyps are protruded, and being, when alive, of a bright grass-green

colour, they contrast very beautifully with the rich crimson of the tubes

they inhabit.

[Illustration: Caryophyllia.]

In our seas, the coralligenous Zoophytarians, distinguished by the hard

calcareous skeletons they deposit within their tissues are but feebly

represented by a few straggling Caryophylliæ, but in the tropical

ocean they branch out into numerous families, genera, and species, and

play a highly important part in the economy of the maritime domain.

Originally proceeding from single ova, which at first freely move by

means of vibratile ciliæ, and become fixed after a short period of

erratic existence, they multiply by gemmation, and grow into an immense

variety of forms, of which the following description by one who has

long and attentively studied them in their native haunts may serve to

give an idea. "Trees of coral," says Professor Dana, "are well known;

and although not emulating in size the oaks of our forests--for they do

not exceed six or eight feet in height--they are gracefully branched,

and the whole surface blooms with coral polyps in place of leaves and

flowers. Shrubbery, tufts of rushes, beds of pinks, and feathery mosses,

are most exactly imitated. Many species spread out in broad leaves or

folia, and resemble some large-leaved plant just unfolding; when alive,

the surface of each leaf is covered with polyp-flowers. The cactus, the

lichen clinging to the rock, and the fungus in all its varieties, have

their numerous representatives. Besides these forms imitating vegetation,

there are gracefully modelled vases, some of which are three or four feet

in diameter, made up of a network of branches and branchlets, and sprigs

of flowers. There are also solid coral hemispheres like domes among the

vases and shrubbery, occasionally ten or even twenty feet in diameter,

whose symmetrical surface is gorgeously decked with polyp-stars of purple

and emerald-green."

Under such aspects appear the living organisms whose combined efforts

have mainly constructed those reefs and islands of coral origin which

now lie scattered far and wide over the surface of the equatorial ocean.

Words are inadequate to express the splendour of the submarine gardens

with which the lithophytes clothe the rocky shores of the tropical seas.

"There are few things more beautiful to look at," says Captain Basil

Hall, "than these corallines when viewed through two or three fathoms

of clear and still water. It is hardly an exaggeration to assert that

the colours of the rainbow are put to shame on a bright sunny day by

what meets the view on looking into the sea in those fairy regions." And

Ehrenberg was so struck with the magnificent spectacle presented by the

living polyparia in the Red Sea that he exclaimed with enthusiasm, "Where

is the paradise of flowers that can rival, in variety and beauty, these

living wonders of the ocean!"

Besides the charms of their own growth, the tropical coral gardens afford

a refuge or a dwelling-place to numberless animals clothed in gorgeous

apparel. Fishes attired in azure, scarlet, and gold, crustaceans,

sea-urchins, sea-stars, sea anemones, annelides, of a brilliancy of

colour unknown in the northern seas, glide or swim along through their

tangled shrubberies; and frequently the gigantic tridacna, embedded in

their calcareous parterres, discloses, on opening her ponderous valves,

her violet mantle tinted with emerald-green. The enchanted naturalist

lingers for hours over the magnificent spectacle, and forgets the lapse

of time, as wonders upon wonders crowd on his enraptured gaze.

But the tropical coral-gardens serve not only as a harbour of refuge

to the numberless creatures that frequent their labyrinthine recesses,

for many annelides, crustaceans, asterias, and even fishes, feed upon

their animal flowrets. Among these, the Scari are provided with a very

remarkable dental apparatus to protect their mandibles from injury

while biting the calcareous corals. These fishes have their jaws,

which resemble the beak of a parrot (whence they receive their usual

appellation "parrot fishes"), covered externally with a kind of pavement

of teeth, answering the same purpose as the horny investment of the

mandibles of the bird. The teeth that form this pavement are perpetually

in progress of development towards the base of the jaw, whence they

advance forward, when completed, to replace those which become worn away

in front by the constant attrition to which they are subjected. Thus

armed, the Scari browse without difficulty on the newest layers of the

stony corals, digesting the animal matter therein contained, and setting

free the carbonate of lime in a chalky state. Many of the Diodons,

Chætodons, and Balistæ or file-fishes, of which Kittlitz saw some new

species, one still more splendid than the other, in every lagoon-island

he visited in the long range of the Carolines, likewise feed upon corals,

and possess a dental apparatus fit for masticating their refractory

aliment. The Diodons have grooved teeth, excellently adapted to crush and

bruise, and the Balistæ have eight strong conical teeth in every jaw,

with which they easily nip off the shoots of the coral bushes.

Of the reef-building corals it may well be said that they build for

eternity. The bones of the higher animals vanish after a few years, but

the stony skeleton of the polyp remains attached to the spot of its

formation, and serves as a basement or stage for new generations to

build upon. Life and death are here in concurrent or parallel progress;

generally the whole interior of a corallum is dead. The large domes of

the astræas are in most species covered with a hemispherical living

shell, about half an inch thick; and in some porites of the same size the

whole mass is lifeless, except the exterior for a sixth of an inch in

depth.

[Illustration: Astræa.]

We are astonished when travellers tell us of the vast extent of certain

ancient ruins; but how utterly insignificant are the greatest of these

when compared with the piles of stone accumulated in the course of ages

by these minute, and individually so puny architects! The history of

the formation of coral-reefs is no less wonderful than their extent.

They have been divided, according to their geological character, into

three classes. The first fringes the shores of continents or islands

(shore-reefs); the second, rising from a deep ocean, at a greater

distance from the land, encircles an island, or stretches like a barrier

along the coast (encircling-reefs, barrier-reefs); the third, enclosing

a lagoon, forms a ring or annular breakwater round an interior lake

(atolls, or lagoon-islands).

[Illustration: Stone Corals.]

Many of the high rocky islands of the Pacific lie, like a picture in

its frame, in the middle of a lagoon encircled by a reef. A fringe of

low alluvial land in these cases generally surrounds the base of the

mountains; a girdle of palm-trees, backed by abrupt heights, and fronted

by a lake of smooth water, only separated from the deep blue ocean by

the breakers roaring against the encircling reef; such, for instance, is

the scenery of Tahiti, so justly named "the queen of islands." But the

encircling reefs are often at a much greater distance from the shore.

Thus in New Caledonia they extend no less than 140 miles beyond the

island.

As an example of barrier-reefs, I shall cite that which fronts the

north-east coast of Australia. It is described by Flinders as having a

length of nearly a thousand miles, and as running parallel to the shore

at a distance of between twenty and thirty miles from it, and in some

parts even of fifty and seventy. The great arm of the sea thus inclosed,

has a usual depth of between ten and twenty fathoms. This probably is

both the grandest and most extraordinary reef now existing in any part of

the world.

[Illustration: Stone Corals.]

The atolls, or lagoon-islands, are numerously scattered over the face

of the tropical ocean. The Marshall and Caroline islands, the Paumotic

group, the Maldives and Lacadives, and many other groups or solitary

islets of the Pacific or Indian Ocean, are entirely built up of coral;

every single atom, from the smallest particle to large fragments of

rock, bearing the stamp of having been subjected to the power of organic

arrangement. A narrow rim of coral-reef, generally but a few hundred

yards wide, stretches around the enclosed waters. When a lagoon-island

is first seen from the deck of a vessel, only a series of dark points is

descried just above the horizon. Shortly after, the points enlarge into

the plumed tops of cocoa-nut trees, and a line of green, interrupted at

intervals, is traced along the water's surface.

The long swell produced by the gentle but steady action of the trade

wind, always blowing in one direction over a wide area, causes breakers

which even exceed in violence those of our temperate regions, and which

never cease to rage. It is impossible to behold these waves without

feeling a conviction that a low island, though built of the hardest rock,

would ultimately yield, and be demolished by such irresistible forces.

Yet the insignificant coral-islets stand and are victorious; for here

another power, antagonistic to the former, takes part in the contest.

The organic forces separate the atoms of carbonate of lime one by one

from the foaming breakers, and unite them in a symmetrical structure. Let

the hurricane tear up its thousand huge fragments, yet what will this

tell against the accumulated labours of myriads of architects at work

night and day, month after month. Thus do we see the soft and gelatinous

body of a polyp, through the agency of vital laws, conquering the great

mechanical power of the waves of an ocean, which neither the art of man

nor the inanimate works of nature could successfully resist.

The reef-building corals, so hardy in this respect, are extremely

sensitive and delicate in others. They absolutely require warmth for

their existence, and only inhabit seas the temperature of which never

sinks below 60° Fahr. They also require clear and transparent waters.

Wherever streams or currents are moving or transporting sediment, there

no corals grow, and for the same reason we find no living zoophytes upon

sandy or muddy shores.

As within one cast of the lead coral-reefs rise suddenly like walls from

the depths of ocean, it was formerly supposed that the polyps raised

their structures out of the profound abysses of the sea; but this opinion

could no longer be maintained, after Mr. C. Darwin and other naturalists

had proved that the lithophytes cannot live at greater depths than twenty

or at most thirty fathoms.

Hereupon Quoy and Gaimard broached the theory that corals construct their

colonies on the summits of mountain ridges, or the circular crests of

submarine craters, and thus accounted both for the great depths from

which the coral-walls suddenly rise, and the annular form of lagoon

islands. Yet this theory, ingenious as it was, could not stand the test

of a closer examination: for no crater ever had such dimensions as, for

instance, one of the Radack Islands, which is fifty-two miles long by

twenty broad; and no chain of mountains has its summits so equally high,

as must have been the case with the numerous reef-bearing submarine

rocks, considering the small depth from which the lithophytes build.

Another seemingly inexplicable fact was, that, although corals hardly

exist above low-water mark, reefs are found at Tongatabu or Eua, for

instance, at elevations of forty and even three hundred feet above the

level of the ocean.

Mr. Charles Darwin was the first to give a satisfactory explanation

of all the phenomena of coral formations, by ascribing them to the

oscillations of the sea bottom, to its partial upheaving or subsidence.

It is now perfectly well known that large portions of the continent of

South America, Scandinavia, North Greenland, and many other coasts, are

slowly rising, and that other terrestrial or maritime areas are gradually

subsiding. Thus on every side of the lagoon of the Keeling Islands, in

which the water is as tranquil as in the most sheltered lake, Mr. Darwin

saw old cocoa-nut trees undermined and falling. The foundation-posts of

a store-house on the beach, which, the inhabitants said, had stood seven

years before just above high water, were now daily washed by the tide.

Supposing on one of these subsiding areas an island-mountain fringed with

corals, the lithophytes, keeping pace with the gradual sinking of their

basis, soon raise again their solid masses to the level of the water; but

not so with the land, each inch of which is irreclaimably gone. Thus the

fringing reef will gradually become an encircling one; and, if we suppose

the sinking to continue, it must by the submergence of the central land,

but upward growth of the ring of coral, be ultimately converted into a

lagoon-island.

The numerous _atolls_ of the Pacific and Indian Ocean give us a far

insight into the past, and exhibit these seas overspread with lofty lands

where there are now only humble monumental reefs dotted with verdant

islets. Had there been no growing coral, the whole would have passed

away without a record; while, from the actual extent of the coral-reefs

and islands, we know that the entire amount of the high land lost to

the Pacific was at least 50,000 square miles. But as other lands may

have subsided too rapidly for the corals to maintain themselves at the

surface, it is obvious that the estimate is far below the truth.

As living coral-reefs do not grow above low-water mark, it may well be

asked how habitable islands can form upon their crests. The breakers

are here the agents of construction. They rend fragments and blocks

from the outer border of the reef and throw them upon the surface.

Corals and shells are pulverised by their crushing grinding power,

and gradually fill up the interstices. In this manner the pile rises

higher and higher, till at last even the spring tides can no longer wash

over it into the lagoon, on the border of which the fine coral sand

accumulates undisturbed. The seeds which the ocean-currents often carry

with them from distant continents find here a congenial soil, and begin

to deck the white chalk with an emerald carpet. Trees, drifting from the

primeval forest, where they have been uprooted by the swelling of the

river on whose banks they grew, are also conveyed by the same agency to

the new-formed shore, and bring along with them small animals, insects,

or lizards, as its first inhabitants. Before the stately palm extends

its feathery fronds sea-birds assemble on this new resting-place, and

land-birds, driven by storms from their usual haunts, enjoy the shade

of the rising shrubbery. At last, after vegetation has completed its

work, man appears on the scene, builds his hut on the fruitful soil

which falling leaves and decaying herbs have gradually enriched, and

calls himself the master of this little world. In this manner all the

coral-reefs and islands of the tropical seas have gradually become

verdant and habitable; thus has arisen the kingdom of the Maldives, whose

sultan, Ibrahim, glories in the title of sultan of the thirteen atolls

and twelve thousand isles. May his shadow never be less!

CHAP. XVIII.

PROTOZOA.

The Foraminifera.--The Amœbæ--Their Wonderful Simplicity of

Structure.--The Polycystina.--Marine Infusoria.--Sponges--Their

Pores--Fibres and Spiculæ--The Common Sponge of Commerce.

Think not, reader, that the life of the ocean ends with the innumerable

hosts of fishes, molluscs, crustacea, medusæ, and polyps we have

reviewed, and that the waters of the sea or the sands of the shore have

now no further marvels for us to admire. The naked eye indeed may have

attained the limits of life, but the microscope will soon reveal a new

and wonderful world of animated beings.

Take only, for instance, while wandering on the beach, a handful of

drift-sand, and examine it through a magnifying glass. You will then not

seldom find, among the coarser grains of inorganic silica, a number of

the most elegant shells; some formed like ancient amphoræ, others wound

like the nautilus, but all shaped in their minuteness with a perfection

which no human artist could hope to equal in the largest size.

[Illustration: Nummulina discoidalis.

_a._ Natural size.

_b._, _c._ The same, highly magnified.

]

The knowledge of these charming little marine productions is of modern

date, for they were first observed in the sand of the Adriatic by

Beccaria in 1731, and for some time believed to belong exclusively to

that gulf. At a later period some species were discovered here and there

in England and France, but their universality and importance in the

economy of the ocean were first pointed out in 1825, by the distinguished

French naturalist Alcide d'Orbigny.

The sand of many sea-coasts is so mixed with Foraminifera, as they have

been called from the openings with which their shells are pierced, that

they often form no less than half its bulk. Plancus counted 6000 in an

ounce of sand from the Adriatic, and d'Orbigny reckoned no less than

3,849,000 in a pound of sand from the Antilles. Along the whole Atlantic

coast of the United States, the plummet constantly brings up masses

of foraminiferous shells from a depth of ninety fathoms, so that the

vast extent of ocean-bottom, which itself forms but a small part of the

domains they occupy, is literally covered with their exuviæ.

Thus their numbers surpass all human conception, nor can any other series

of beings be compared to them in this respect; not even the minute

crustaceans which colour thousands of square miles on the surface of the

sea, and, according to Scoresby, form almost exclusively the food of

the huge Greenland whale; nor the infusory animals of the fresh-water,

whose shields compose the Bilin slate quarries in Bohemia; for these are

limited in their distribution, whereas the Foraminifera occur in all

parts of the world.

[Illustration: Amœba.]

[Illustration: Amœba, showing the extemporaneous feet formed by

evanescent projections of the general plastic mass of the animal.]

The resemblance of the Foraminifera to the nautili and ammonites at first

led naturalists to suppose that they formed part of the same class, which

in a long course of centuries had dwindled down in less congenial seas

to almost invisible dimensions; but a closer investigation proved them

to belong to a much lower order of beings, nearly related to the Amœbæ,

which likewise occur all over the ocean. Other animals excite our wonder

by their complicated structure, but the amœba raises our astonishment by

the excessive simplicity of its organisation. The amœba is nothing more

than a living globule of mucus, a transparent, colourless, contractile

substance, or plastic mass, the individual life of which shows itself in

manifold changes of form, bearing the character of voluntary motion. When

an amœba approaches another minute animal or plant unable to move out of

its reach, it sends out extemporaneous feet, which soon clasp the prey

on all sides, and the prisoner lies embedded in the living mucus until

all his soluble parts have been absorbed. There is absolutely no trace of

particular organs in the amœba; all its constituent particles may be used

for any purpose, all equally move and digest, and each can at any time

perform the organic functions pertaining to the whole.

[Illustration: A Compound Foraminiferous Protozoon, magnified.

The shell is perforated with holes, through which the different lobes

of the animal communicate, and thread-like portions are protruded

externally.]

In their internal simplicity the Foraminifera are on a par with the

amœbæ, and differ from them only in respect of their outward form. The

amœbæ are naked, while the Foraminifera are covered with a shell, out

of which, through one or numerous openings, the animal protrudes the

processes which it requires for creeping or seizing its prey. These

processes or filaments of mucus frequently ramify, closing as they

spread, and sometimes covering an area of several lines in diameter, in

the centre of which the animal inclosed in its shell waits for its prey,

like a spider in its net.

The extended filaments appear to have something venomous about them;

for Dr. Schultze, to whom we owe an interesting monograph on the

Foraminifera, frequently saw small and sprightly parameciæ, colpodes, and

other infusoria drop down paralysed as soon as they touched the net.

[Illustration: Various forms of Foraminifera.

_a. Lagena striata._

_a′. Nodosaria rugosa._

_b. Marginulina raphanus._

_b′._ Longitudinal section of shell of ditto.

_c. Polystomella crispa_, with its pseudopodia protruded.

_d. Nummulites lenticularis_, shown in horizontal section.

_e. Cassidulina lævigata._

_f. Textularia globulosa._

_g. Miliolina seminulum._

_g′._ Animal of Miliolina removed from its shell.

]

The amazing variety of form of the Foraminifera is no less remarkable

than the elegance of their delicately chiselled shells, and may well be

called immense, as no less than 2,400 living and fossil species have

already been distinguished by naturalists, and a far greater number is

probably still nameless and unknown. Though generally so minute that the

diameter of the pores through which they protrude their filaments usually

only ranges from 1/3000 to 1/10000 of an inch yet the diminutive world

of the Foraminifera has also its giants, particularly among the fossil

species, such as the Nummulites, which occur in such prodigious numbers

in the limestone of the Egyptian pyramids, and whose flattened lenticular

coin-like forms (d) attain the comparatively gigantic diameter of several

inches. Thus the material with which the proud Pharaohs of the Nile

constructed their colossal tombs was originally piled up at the bottom of

the sea by countless generations of shell-cased Protozoa.

The Foraminifera are among the oldest inhabitants of our globe,[T] and

as the present ocean contains them in countless multitudes, thus have

they swarmed in the waters of the primeval seas from the first dawn of

creation, and piled up the monuments of their existence in vast strata

of limestone. A great part of the rocky belt from Rügen to the Danish

isles, the white chalk cliffs which, beginning in England, extend through

France as far as Southern Spain, are chiefly composed of the shells

of Foraminifera, and the zone of Nummulite limestone, which served to

build the huge quadrilateral monument of Cheops, forms a band, often

1,800 miles in breadth, and frequently of enormous thickness, from the

Atlantic shores of Europe and Africa through Western Asia up to North

India and China; enough to satisfy the most extravagant architectural

folly of millions of despots. So important is the part which these

beings, individually so minute, have performed and still perform in the

geological annals of the globe.

[Footnote T: The _Eozoon canadense_, the oldest of known organic remains,

found in the Upper Laurentian series, which preceded the Cambrian

formation, is a Foraminifer. Millions of years must have passed since it

first felt and moved.]

Many of these "minims of nature" consist of only one chamber, and

hence are called unilocular or monothalamous; but a vast proportion

consist of several chambers, and hence are called multilocular or

polythalamous. The latter, however numerous their chambers or seemingly

complex their structure, always originate as a single shell. The

primitive jelly-sphere, or first sarcode segment, secretes around itself

its appropriate calcareous envelope. Having grown too large for its

habitation, it protrudes a portion of itself without, and thus forms

a second segment. If by a process of spontaneous fission this segment

becomes quite detached from its parent, and repeats the life and method

of reproduction of the latter, a series of monothalamous shells will be

formed. But if by means of a sarcode band the primitive segment maintains

its connection with its immediate offspring, and this, repeating the

reproductive process, does the same, a compound shell will, of course, be

the result.

Among the microscopic denizens of the ocean, the Polycystina rival the

Foraminifera both by their number and their wonderful elegance of form

and structure. Their body consists of the same viscid homogeneous plastic

mass, termed "sarcode" by the naturalists; like them they are capable of

protruding it through the foramina with which their shell is pierced,

and consequently they are ranked with them among the Rhizopods, or

root-footed animalcules, that form the lowest order of the Protozoa, the

lowest class of the animal world.

[Illustration: Polycystina.

_a. Podocyrtis Schomburgkii. b. Haliomma Humboldtii._]

It is a peculiar feature of these beautiful little shells (whose delicate

sculpture frequently reminds the observer of the finest specimens of

the hollow ivory balls carved by the Chinese) that they are usually

surmounted by a number of spine-like projections, very frequently having

a radiate disposition. Some have an oblong shape (Podocyrtis), others a

discoid form (Haliomma), from the circumference of which the silicious

spines project at regular intervals, so as to give them a star-like

aspect. They are generally of a smaller size than even the Foraminifera,

appear to be almost as widely diffused, and have also largely contributed

to the structure of the earth-rind. They were first discovered by

Professor Ehrenberg at Cuxhaven, on the North Sea; they were afterwards

found by him in collections made in the antarctic seas, and have been

brought up by the sounding lead from the bottom of the Atlantic at depths

of from 1,000 to 2,000 fathoms.

The term Infusoria, which formerly comprised a most heterogeneous

assemblage of minute plants and animals, is now confined to the highest

order of the Protozoa, distinguished from the Rhizopods by the possession

of a mouth and of ciliary filaments, whose vibrations serve them both

for progression through the water and for drawing alimentary particles

into the interior of their body. Though most of the Infusoria live in

ponds, morasses, pools, wells, or cisterns, yet many are marine, as, for

instance, the _Carchesium polypinum_, which is frequently found attached

to corallines, and the _Vaginicola valvata_, which from its sheath and

valve strongly reminds one of a tubicolar annelide.

[Illustration: Marine Infusoria.

_a._ _Vaginicola valvata_, showing animal extended, and

valve (φ) raised.

_a′._ The same, showing animal contracted within its sheath, and

valve (φ′) shut down.

_b._ _Lagotia viridis_, showing rotatory organ (ξ).

_b′._ Young animal of preceding.

]

The wide diffusion both in time and space of the marine Protozoa, and

chiefly of the Foraminifera and Polycystina, is a sufficient proof of

their vast importance in the household of the seas. Along with the

Diatoms and other microscopical forms of vegetation on which their own

existence depends, they evidently constitute the basis on which the

superstructure of all the higher orders of the animal life of the ocean

reposes. Hosts of minute crustaceans, annelides, acalephæ, and molluscs,

feed upon their inexhaustible legions, and serve in their turn to sustain

creatures of a larger and still larger size until finally Man is enabled

to feast on the abundance of the seas.