The Ocean World: Being a Description of the Sea and Its Living Inhabitants.

It is a singular fact that the creature notably changes colour under any exertion, so that the animal at rest and in motion are two different beings. When walking under water the tube is directed behind, its arms are spread out, the head is raised, and the body slightly inclined forward; its mantle is then of a pearly grey, and the spots take the tint of wine lees. When at rest the shades disappear.

The Pinnoctopus (Fig. 325), another genera of this family, have the body oblong, with lateral expansions, as represented in the accompanying figure.

In Cirrotheutis the arms are completely united in their whole extent by a thin membrane furnished with cirri, which alternate with certain suckers arranged in one row. Only one species of this genera is known as an inhabitant of northern seas, which is represented in Fig. 326.

The sixth family, Argonautidæ, contains only Argonauta.

The Argonauta, or Paper-nautilus. Floating gracefully on the surface of the sea, trimming its tiny sail to the breeze, just sufficient to ruffle the surface of the waves, behold the exquisite living shallop. The elegant little bark which thus plays with the current is no work of human hands, but a child of Nature: it is the Argonaut, whose tribes, decked in a thousand brilliant shades of colour, are wanderers of the night in innumerable swarms on the ocean's surface.

The marine shell which Linnæus called the Argonaut enjoyed great renown among the ancient Greeks and Romans. It was the subject of graceful legends; it had inspired great poets; it occupied the attention of Aristotle, who called it the Nautilus and Nauticos, and of Pliny, who called it Pompylius. Few animals, indeed, have been so celebrated, so anciently known. The Greek and Roman poets saw in it an elegant model of the ship which the skill and audacity of the man constructed who first braved the fury of the waves; in the words of the poet, "armour of triple oak and triple brass covered the heart of him who first confided himself in a frail bark to the relentless waves:"

To meet the Pompylius was, according to the superstitious Roman, a favourable presage. This little oceanic wanderer, in spite of the capricious waves, was a tutelar divinity, who guarded the navigator in his course, and assured him of a happy passage. Listen to the immortal author of the first Natural History of Animals, the philosophical Aristotle. "The Nautilus Polyp," says the learned historian, "is of the nature of animals which pass for extraordinary, for it can float on the sea; it raises itself from the bottom of the water, the shell being reversed and empty, but when it reaches the surface it readjusts it. It has between the arms a species of tissue similar to that which unites the toes of web-footed birds. When there is a little wind, it employs this tissue as a sort of rudder, letting it fall into the water with the arms on each side. On the approach of the least danger it fills its shell with water, and sinks into the sea."

Pliny gives it the name of Pompylius, and, after the example of Aristotle, explains how it navigates, by elevating its two first arms, a membrane of extreme tenuity stretching between them, while it rows with the others, using its median arm as a rudder. The Greek poet, Oppian, who lived in the second century of our era, and to whom we are indebted for Poems on Fishing (Halieutica) and the Chase (Cynegetica), says of it: "Hiding itself in a concave shell, the Pompylius can walk on land, but can also rise to the surface of the water, the back of its shell upwards, for fear that it should be filled. The moment it is seen, it turns the shell, and navigates it like a skilful seaman: in order to do this, it throws out two of its feet like antennæ between which is a thin membrane, which is extended by the wind like a sail, while two others, which touch the water, guide, as with a rudder, the house, the ship, and the animal. If danger approaches, it folds up its antennæ, its sail, and its rudder, and dives, its weight being increased by the water which it causes to enter the shell. As we see a man who is victor in the public games, his head circled by a crown, while vast crowds press around, so the Pompylius have always a crowd of ships following in their track, whose crews no longer dread to quit the land. O fish justly dear to navigators! thy presence announces winds soft and friendly: thou bringest the calm, and thou art the sign of it."

Oppian carried his admiration a long way. That the Argonaut is an animated skiff is agreed on all hands; but, in making it almost a bird—in according to it at once the faculty of gracefully navigating the sea and floating in the atmosphere as an inhabitant of the regions of air—he was passing the limits permissible to poetic license.

But the properties of the Nautilus has not alone struck the imagination of the Greeks and Romans; it also attracted the attention of the Chinese, who call it the boat-polyp. Rumphius informs us, that in India the shell fetches a great price (Fig. 327). Women consider it a great, a magnificent ornament. In their solemn fêtes dancers carry one of these shells in the right hand, holding it proudly above their heads. Nor did it require the dithyrambic praises with which the ancients have surrounded it to recommend it to the admiration of modern naturalists. Without exaggerating the graceful attributes with which it is gifted, it is at once one of the most curious objects in Nature.

Its body (Fig. 328) is ovoid in form, and it is furnished with eight tentacles, covered with a double row of suckers. Of these tentacles, six are narrow and slender, tapering to a point towards the extremity, while two of them expand toward the extremity in the form of wings or sails. These are all folded up when in a state of repose. The body itself is contained in a thin, white, and fragile univalve shell, which is oval, flattened on the exterior, but rolled up in a spiral in the interior, the last turn of the shell being so large as to give it something of the form of an elegantly-shaped shallop. Singularly enough, the body of the animal does not penetrate to the bottom of the shell, nor is it attached to it by any muscular ligament; nor is the shell moulded exactly upon it, as is the case with most other testaceans.

What does all this imply? Is the Argonaut a parasite? a fraudulent disinheritor? a vile assassin, who, having surprised and killed the legitimate proprietor of the shell, has installed itself in its place, and in the proper house of its victim? Such crimes are not without example in the natural history of animals—witness the proceedings of the curious hermit crab, whose proceedings we shall glance at in a future chapter. The parasitic character of the Nautilus was long conceded by naturalists; but recent facts have corrected this opinion. We have collected their shells, of all dimensions and of all ages, inhabited always by the same animal, whose size is always proportioned to the volume of the shell. More than that, it is now known that in the egg of the Nautilus the rudiments of the shell exist. M. Chenu tells us, that under the microscope Professor Duvernoy discovered a distinct shell contained in the embryo. Sir Everard Home asserts the contrary; and no opportunity presented itself for the complete solution of the question, until Poli was placed by the King of Naples in a position to solve it. The piscina of Portici was placed at his disposal. He witnessed the curious mechanism by which the egg is expelled from the uterus, having a shell, and satisfied himself, by following their development day by day, that the shell existed in the embryo, and grew with the animal. He satisfied himself also that the opinion enunciated by Aristotle, that at no point did the animal adhere to the shell, was perfectly true.

Finally, in the curious series of experiments carried on by Madame Power, in the port of Messina, the fragments of the frail bark of the mollusc, which were broken off in taking it, were restored in a few days, having been reproduced. It is, therefore, quite demonstrated that the Nautilus, like other testaceous molluscs, itself secretes and constructs its shell—its diaphanous skiff. The reader, however, must not flatter himself that he can witness with his own eyes from the shore, in our narrow channel, the charming picture of the Nautilus painted by poets and natural historians: they never come near the shore. They are timid and cautious creatures, dwelling almost always in the open sea. They live in families, some hundreds of miles from the shore; and it is during the night, or at most in the fading light of sunset, that they assemble together to pursue their gambols on the surface of a tranquil sea.

However reluctant we may be to destroy the marvellous fictions of ancients and moderns, we are compelled to declare that there is no truth in the often-repeated statement that the Nautilus uses its palmated arms as oars or sails. In order to swim on the surface, it comports itself as all other Cephalopods do. It uses neither oars nor sails, and the palmate arms only serve to envelop and retain its hold on its frail shell. Its principal apparatus of progression is the locomotive tube with which it is furnished, in common with all Cephalopods, and which is in the Nautilus very long. Aided by this apparatus, it ejects the water after it has served the purpose of respiration, and, in doing so, projects itself against the liquid, as it were. While it advances through the water under this impulse, its pendent arms, elongated and reunited in bundles, extend the whole length of the shell. Fig. 329 shows the position of the different parts of the animal when it thus breasts the waves. These arms are also powerful aids when the animal creeps on the ground at the bottom of the sea.

When the animal is disturbed it retires completely into its shell. From that moment, the equilibrium being changed, the shell is overturned, and the animal is nearly invisible. If frightened, it entirely submerges itself, and sinks to the bottom.

These little beings share with other Cephalopods the strange faculty of changing colour under the influence of some vivid impression; but their graceful and delicate organization redeems them from the charge we have brought against the cuttles. The Nautilus can blush, turn pale, and show through its transparent shell its body changing in sudden shades; but it never exhibits those bristling, unpleasant tubercles, the hideous inheritance of the larger and coarser Cephalopods—the tyrants of the sea.

The male Argonauts are very small, often not a tenth part of the size of the females, which alone possess the shells.

The Nautilus carries its egg in the shell, and the little ones are also hatched in this floating cradle. Four species are at present known: the species described by Aristotle and Pliny, and the more ancient naturalists; namely, A. argo, or papyracea (Figs. 327 and 329), which are inhabitants of the Mediterranean as well as the Indian Ocean and the Antilles. Two others, A. tubercula, belonging exclusively to the Indian Ocean, and A. baillant, which is met occasionally in the Pacific and Atlantic Oceans.

The nautilus belongs to the section of Octopoda, and the class of Acetabuliferous Cephalopods, having, as the name indicates, eight feet, from ὀκτὼ, eight, and ποῦς, foot; at the same time the body is entirely fleshy, and without fins. The genera of cuttles (Sepia) and Calmars (Loligo) belong to another section of the same class; namely, the Decapoda, because they have ten feet and a sort of internal osselet, with fins, &c.

THE DISTRIBUTION OF THE MOLLUSCA.

We have thought it better to treat this subject in a separate chapter, for its vast and complicated nature renders it otherwise difficult to handle, except in a space which would exceed the limits of this work.

The different genera of the organic world are peculiar to, or most frequent in, certain localities, and even species and varieties have their limits. This habit pervades the entire range of organisms, from the lowest plants to man, whose qualities are to a great extent the type of the locality he inhabits. The geography of the Mollusca is perhaps the best known to science. The labours of Mr. Louis Agassiz, Dr. Sclater, and Professor Edward Forbes, have done much towards giving us a clear idea of zoological geography. Climate alone is insufficient to account for the distribution of animals: some higher cause rules here. But while we admit this, still we must acknowledge that climate exerts considerable influence in modifying the qualities of species.

The distribution of the Mollusca may be considered from three points of view. First, as regards geography; second as regards depth; and third as regards time; the last belongs to geology.

We shall now survey the principal divisions of the ocean; the line of demarcation being drawn, not by latitude or longitude, but by genera and species.

The Mollusca of the Arctic seas are well known to show considerable analogy with those of the later Tertiary periods of Europe. Hence the great interest connected with their comparison, as it affords,—provided we are satisfied with this line of argument,—a proof that an Arctic climate formerly existed in temperate regions. It is the northern Drift of which we are speaking. Even when species are found living in Britain identical with those of the Arctic regions, still there is often a difference in the form or size of British and Arctic specimens; certain species, such as Cyprina Islandica, being comparatively small in the south of Britain, larger in Shetland, and attaining their greatest size in Iceland.

The countries included in the Arctic molluscan province are Lapland, Iceland, Greenland, the west coast of Davis' Straits, and Behring's Straits. About two hundred species are enumerated by the various Arctic voyagers, as found in these seas; of these about one-half are peculiar to these seas, and the other half are either found living in the temperate regions of Europe, or in their so-called glacial strata.

The Boreal province includes the North Atlantic, from Nova Scotia to Iceland, and from thence to Faroe, Shetland, and the Norway coast.

The number of species is very large; and more than one-half are common both to Scandinavia and the North American coast, while a great number also are found on the British coast.

The province called Celtic by Professor Edward Forbes embraces the coasts of Britain, Sweden, and Denmark.

Our British mollusca are about seven hundred in number; those bearing shells are above five hundred. Of these about thirty are peculiar to Britain. The shells of the Baltic are identical with those of this province.

The Lusitanian province stretches from Madeira and the Canaries to the coasts of Spain and Portugal, and includes also the Mediterranean. But as one might expect, on close examination, the Mollusca in so large an area differ so widely that we are forced to admit the existence of great divisions.

The number of species found on the coast of Madeira by Mr. McAndrew was one hundred and fifty-six, of which forty-four per cent. were identical with British species, and eighty-three found near the Canaries.

The shells of the Mediterranean are six hundred in number, but it is probable that more extensive dredging will result in great accessions being made to this list. A very small number of species only are identical with those now found in the West Indies.

Nine genera are peculiar to the Mediterranean.

In the character of its shells, the Black Sea resembles the Mediterranean, but does not contain much more than a tenth of the number of its species. The number of shells found on the Spanish and Portuguese coasts is much smaller than one would expect, and can only be attributed to the scanty explorations that have been made. As we might expect, the number of species identical with those of Northern Europe is much greater on the Atlantic than on the Mediterranean coast of Spain.

The sea of Aral, and the Caspian, contain a few peculiar species; but they have been so little explored, that it is premature, we think, to form them into a province. The proportions of salt contained in these seas is much less than in the ocean.

The west of Africa affords a considerable number of fine shells; the species most numerous being those of Murex, Conus, and Clavatula.

The south African province contains four hundred species; the characteristic genera are Terebratella, Chiton, Patella, Trochus, Fissurella, Cypræa, and Conus. A large number of these species are not found elsewhere.

The Indo-Pacific province stretches from Australia to Japan; the greater part of the east coast of Africa; the Red Sea; Persian Gulf; the Asiatic coast, and the islands of the Indian Archipelago.

The molluscs of the Red Sea remind us of those of India; the percentage of those found also in the Mediterranean being much less. The shells of the Persian Gulf are but little known; one species, the brindled cowry (Cypræa princeps), has been sold for fifty pounds.

The seas of New Zealand and Australia have been formed into a province. As might be anticipated, their mollusca have little in common with those of the rest of the globe.

The Japonic province includes the coast of Japan and the Corea.

The Aleutian province, the centre of which may be taken to be the Aleutian islands, shows great analogy with the Boreal province of the west, a considerable number of the shells being identical—a fact especially interesting when we consider that very few species are found common to both the south-eastern and south-western coasts of America.

The Californian province is very distinct from that of Panama; the most numerous genera found there, are Chiton, Acmæa, Fissurella, Trochus, and Purpura.

The marine shells of Panama are upwards of thirteen hundred; the region included stretches from the Gulf of California to Peru. For our knowledge of this province we are much indebted to the researches of Dr. P. P. Carpenter, who has catalogued six hundred and fifty-four species, as found at Mazattan.

The Peruvian province contains a long list of species, and extends from Callao to Valparaiso.

The Magellanic province includes the extreme south of America and the Falkland Islands. Many genera, the species of which are usually small, here reach an enormous size, and afford, in many cases, the chief animal food consumed by the quadrupeds and human population of that wild and desolate coast.

The Patagonian province extends from St. Catharina to Point Melo on the east coast.

The number of species found also in the Falkland Islands is very small; but a large number are identical with Brazilian species; yet the majority are peculiar.

The Caribbean province extends from Brazil to the West Indies, and includes, also, the northern coast of South America and the Gulf of Mexico; a total of fifteen hundred species is enumerated by Professor Adams as belonging to the province.

The Transatlantic province, or that on the coast of the United States, does not afford a large number of species, only two hundred and thirty being known; of these, only fifteen are found in Europe.

The study of the terrestrial and fresh-water mollusca affords even better grounds for their division into provinces; but we shall not enter into it here, as it belongs to the Land World.

We shall now say a few words on the depth of the sea, or ocean, in which Mollusca are found.

The observations of Milne Edwards, Audonin, and Professor Edward Forbes, have led to the division of the sea into four zones.

The deep sea Coral zone, from fifty to one hundred fathoms; the Coralline zone from fifteen to fifty fathoms; the Laminarian zone, which stretches from fifteen fathoms to low water; and the Littoral zone, between high and low water marks. The great stronghold of Crania, Thetis, Neæra, Yoldia, Dentalium, and Scissurella, is in the deep sea Coral zone; while Buccinum, Fusus, Pleurotoma, Natica, Aporrhais, Philine, and Velutina, which are among the most ravenous and predatory of molluscs, are found in the Coralline zone. They attack the bivalves, whose shells among the relics of former seas, as in those of the present, show evidence of an assault and a murder.

The principal genera of the Laminarian zone are the Nudibranchiata, Aplysia, Trochus, Nacella, Rissoa, and Lacuna, which feed so much on the seaweed of this region.

The Littoral zone, which being accessible as the tide recedes, is best known, affords Cardium, Mytilus, Tellina, Solen, Trochus, Patella, Littorina, and Purpura; or in plain English, cockles, mussels, razor-fish, limpets, periwinkles and tingles;—species which are the first to attract our attention, and which are so much used for food.

CHAPTER XVII.

Passing over the vast numbers of beings which inhabit the debatable ground—the Annelids, which were for ages confounded with the worms, because of their resemblance in form:—a form which might be declared forbidding, but, as Aristotle has well said, Nature, in her domain, knows nothing low, nothing contemptible; the sea-leeches, whose condition was an impenetrable mystery to Pliny, "Omnia incerta ratione, et in naturæ majestate abdita;" and the singular cirripedes, one species of which, the barnacle (Anatifa lævis), was thought by old Gerard, the herbalist, and in his day by many others, to be the egg from which the barnacle goose was produced—passing over these ocean tribes, we reach the Crustaceans—the Insects of the Sea; of greater size, force, and voracity than any land insect with which we are acquainted. They are armed, also, at all points; for, in place of the coriaceous tunic, they are clothed in calcareous armour, both hard and strong, and bristling with coarse hairs, spiny tubercles, and even serrated spines.

The Crustaceans have nearly all of them claws, formidably hooked and toothed, which they employ as pincers, both in offensive and defensive war. They have been compared to the heavily-armed knights of the middle ages—at once audacious and cruel; barbed in steel from head to foot, with visor and corslet, arm-pieces and thigh-pieces—nothing, in fact, is wanting to complete the resemblance.

These marine marauders live on the sea-coast, among the rocks, and near the shore. Some few of them frequent the deep waters, others hide themselves in the sand or under stones, while the common crab (Carcinus mœnas, Leach) loves the shore almost as much as the salt water, and establishes itself accordingly under some moist cliff overhanging the sea, where it can enjoy both.

One of the necessary consequences of the condition of these animals, enclosed in a hard shell, is their power of throwing it off. The solidity of their calcareous carapace would effectually prevent their growth, but at certain determinate periods Nature despoils the warrior of his cuirass; the creature moults, and the calcareous crust falls off, and leaves it with a thin, pale, and delicate tunic. In this state the Crustacean is no longer worthy of its name—its skin has become as vulnerable as that of the softest mollusc; but it has the instinct of weakness—it retires into lonely places, and hides its shame in some obscure crevice, until another vestment, more suitable for resistance, and adapted to its increased size, has been restored.

The Crustacean has not a vertebral column. The covering of the Crustacean consists of a great number of distinct pieces, connected together by means of portions of the epidermis which have not yet become hardened, in the same way as the bones in the skeleton of the vertebrata are connected by cartilages, the ossification of which only takes place in old age. The covering of the Crustacean consists of a series of rings varying in number, the normal number of the body-segments being twenty-one. Each ring is divisible into two arcs—one upper, or dorsal, the other lower, or ventral; and each arc may present four elementary pieces, two of which are united in the mesial line from the tergum, or back; the lower arc is a counterpart of this, while the others form the two side, or epimeral, pieces. The skin, therefore, performs the functions of a skeleton, so that the Crustaceans, as was said by Geoffroy Saint Hilaire, like the molluscs, live inside and not outside the bony column. The analogue of the Crustacea amongst vertebrata is to be found amongst Sturgeonidæ, whose hard, immovable bony case encloses a softer skeleton; agreeing in its characters with that of the higher divisions of vertebrata, although not possessing the solidity of bone.

The Crustaceans vary greatly in colour; some are of a dark, iron-grey, with a dash of steel-blue, like metal weapons forged for combat; a few of them are red, or reddish-brown; others are of an earthy yellow, or of a livid blue.

"The integument," according to Milne Edwards, "consists of a corium, or true skin, and epidermis, with a pigmentary matter, which colours the latter. The corium is a thick, spongy, and vascular membrane, connected with the serous substance which lines the parietal walls of the cavities, as the serous membrane lines the internal cavities among the vertebrata." This pigment is less a membrane than an amorphous matter diffused through the outer layer of the superficial membrane, which changes to red in the greater number of species in alcohol, ether, acids, and water at 212° Fahr.

The calcareous crust of the animal is thick, and in the dorsal region capable of great resistance; their members are also of remarkable hardness; but in the smaller species the shell is often thin, and of that crystalline transparency which permits of its digestion and circulation being observed. Many species, which are quite microscopic, contribute colour to the sea—red, purple, or scarlet: such are Grimothea D'Urvillei and G. gregarea.

Before the year 1823, it was not generally supposed that this class of animals was subject to change of shape from the larva condition, and during its progressive development; but about this time, and for some years following, certain able microscopic experiments clearly demonstrated that a minute nondescript kind of animal called the Zoea Taurus, was nothing more nor less than the young of a kind of Prawn as when extracted from the egg. Mr. Vaughan Thomson, by many successive observations, and under the fire of much adverse criticism, satisfactorily established the truth of metamorphic change in many genera, and, in particular, in regard to the common crab (Cancer pagurus); having succeeded in hatching the ova of this species, the product of which were fine Zoeas. That there are variations in the channel of this law of change has been admitted, but that generally a metamorphosis exists, analogous to that of insects, in the various genera of Crustacea, with hardly an exception, has been clearly established.

The recorded observations of the eminent naturalist we have mentioned, Mr. Thomson, as well as those of Mr. Couch, of Penzance, Mr. Milne Edwards, and particularly those of the last mentioned, the learned author of perhaps the best work extant on the Crustacea, are referred to as treating most lucidly on this interesting subject.

As an illustration of this metamorphosis, we give figures of the Zoea Taurus in two states, viz., Fig. a, in the first stage; and second, Fig. b, as the animal appeared on the fourth day after the first microscopic examination, and when it resolved itself into a kind of prawn. The drawings appear in Mr. Bell's "History of British Stalk-eyed Crustacea," and were taken by that gentleman from the work of a Dutch naturalist, named Slabber, who made the original observation in the year 1768, and published the result in 1778, from which time the subject had been allowed to fall asleep until revived by Mr. Thomson.

Among the sea-spiders, which have no neck (Cephalothorax), the head gradually disappears in the breast, but the belly remains distinct; the middle of the body is compressed, the shape narrow and graceful. Among the Crustaceans which have neither neck nor shape, the head, the breast, and the belly form only one mass, often short, squat, athletic, and difficult to take, as in Pisa tetraodon (Fig. 332), the four-horned spider-crab.

Many of these animals have a powerful tail, consisting of a certain number of ciliated paddles, which it uses in swimming to beat the water, and to confuse its enemies.

The Crustaceans, so far as they are aquatic, respire by means of branchiæ, or gills. In the larger species these branchiæ are lamellous, or with filaments, whose supports are traversed by two canals, one of which leads the blood into the general economy, the other directs it towards the heart. These organs are enclosed in the body. In the smaller species the branchiæ often appear exteriorly, hanging in the water like a fungus. Sometimes these are at once swimming and breathing organs; in other cases the animal has no special organs of respiration.

Nearly all the Crustaceans are strong, hardy, and destructive, forming a horde of nocturnal brigands—merciless marauders, who recoil from no trap in which they can lie in wait for their prey. They fight à l'outrance not only with their enemies, but often among themselves, either for a prey or for a female, sometimes for the sake of the fight. The miserable creatures struggle audaciously with their claws. The carapace generally resists the most formidable blows; but the feet, the tail, and, above all, the antennæ, suffer frightful mutilation. Happily for the vanquished, the mutilated members sprout again after a few weeks of repose. This is the reason for the many Crustaceans met with having the talons of very unequal size: the smaller are those lost in battle replaced. Nature has willed that the Crustacean should not long remain an invalid. They soon return cured of their wounds. "We have seen lobsters," says Moquin-Tandon, "which have in an unfortunate rencounter lost a limb, sick and debilitated, reappear at the end of a few months with a perfect limb, vigorous, and ready for service. O Nature, how thou fillest our souls with astonishment and wonder!"

On the Spanish coast there is a species of crab, known, singularly enough, by the name of Boccaccio; it is caught for its claw, which is considered excellent eating. This is cut off, and the mutilated animal is thrown into the sea, to be taken at some future time when the claw has reappeared.

Crustaceans are nearly all carnivorous, and eat eagerly all other animals, whether living or dead, fresh or decomposed. Little think they of the quality or condition of their food. It is amusing to witness the address and gravity with which the common crab, when it has seized an unfortunate mussel, holds the valve open with one claw, while with the other it rapidly detaches the animal, carrying each morsel to the mouth, as one might do with the hand, until the shell is entirely empty. The crab does not kill its prey directly, like the lobster; it is swallowed also, but with greater appreciation.

M. Charles Lespés surprised upon the shore at Royan a shoal of crabs at their repast. This day they seem to have dined in common, and "God knows the enjoyment," as the good Fontaines said. They were in rows, every head turned to the same side, and nearly on end on their eight feet. They seized the small objects on the shore, which were carried to the mouth, each hand in its turn in regular order: when the right hand reached the mouth the left was on the ground. Let us just figure to oneself a company of disciplined soldiers messing together at the same table!

The Long-horned Corophius (Corophium longicorne), remarkable for its long antennæ, knows perfectly well how to cut the byssus by which the mussels suspend themselves, in order that the bivalve may fall on the weeds among them. Other Crustaceans, also great oyster-eaters, have the cunning or instinct to attack the mollusc without exposing themselves to danger. When the bivalve half opens its shell to enjoy the rays of the sun or take food, the evil-disposed Crustacean slips a stone between the valve. This done, it devours the poor inhabitant of the shell at its leisure.

The Corophius, respecting whom this question is hazarded, are extremely numerous on the shores of the Atlantic towards the end of summer and autumn. They make constant war upon certain marine worms. Off the coast of La Rochelle they may be seen in myriads beating the muddy bottom with their long antennæ in search of their prey. Sometimes they meet one of these Nereida or Arenicola many times their own size, when they unite in a body to attack it. In the oyster beds of La Rochelle they are useful friends to the oyster by destroying these enemies, although they do not hesitate to attack the mollusc when it comes in their way. During the winter the mud of the bouchots gets piled up in unequal heaps, and when the warm season returns, it has become hard and unfit for the cultivation of the mollusc. It is necessary to level and dry these mud-heaps—a process which would be both difficult and costly. Well, the Corophia charge themselves with the task. They plough up annually many square leagues covered with these heaps. They dilute the mud, which is carried out by the ebbing tide, and the surface of the bay is left smooth, as it was in the preceding autumn.

We have said that the Crustaceans do not even respect each other; the larger of the same species often devour the smaller. Rara concordia fratrum! Mr. Rymer Jones relates that he had on one occasion introduced six crabs (Platycarcinus pagurus) of different size into an aquarium. One of them, venturing towards the middle of the reservoir, was immediately accosted by another a little larger, which took it with its claws as it might have taken a biscuit, and set about breaking its shell, and so found a way to its flesh. It dug its crooked claws into it with voluptuous enjoyment, appearing to pay no attention to the anger and jealousy of another of its companions, which was still stronger and as cruel, and advanced towards them. But, as Horace says—and he was not the first to say it—"No one is altogether happy in this lower world":

"Nihil est ab omni parte beatum."

Our ferocious Crustacean quietly continued its repast, when its companion seized it exactly as it had seized its prey, broke and tore it in the same fashion, penetrating to its middle, and tearing out its entrails in the same savage manner. In the mean time the victim, singularly enough, did not disturb itself for an instant, but continued to eat the first crab bit by bit, until it was itself entirely torn to pieces by its own executioner—a remarkable instance at once of insensibility to pain and of cruel infliction under the lex talionis. To eat and to be eaten seems to be one of the great laws of Nature.

Though essentially carnivorous, the Crustaceans sometimes eat marine vegetables. Many even seem to prefer fruit to animal food. Such is the robber-crab (Birgus latro) of the Polynesian Isles, which feeds almost exclusively on the cocoa-nut. This crab has thick and strong claws; the others are comparatively slender and weak. At first glance it seems impossible that it could penetrate a thick cocoa-nut surrounded by a thick bed of fibre and protected by its strong shell; but M. Liesk has often seen the operation. The crab begins by tearing off the fibre at the extremity where the fruit is, always choosing the right end. When this is removed, it strikes it with its great claws until it has made an opening; then, by the aid of its slender claws, and by turning itself round, it extracts the whole substance of the nut.

The Crustaceans have eyes of two kinds—simple and compound: the first are sessile and immovable, and very convex; the other borne on a short calcareous stem or peduncle, and formed of a number of small eyes symmetrically agglomerated—the reunion of all the microscopic cornea of a composite eye, resembling in shape a cap formed of facets. It is said, for instance, that the eye of the lobster consists of 2500 of these little facets. The simple eyes are myopus, or short-sighted—the compound eyes for more distant but perfect sight. They appear to have a strong sense of smell. Many of them cannot swim, but walk with more or less facility at the bottom of the water. It is said, for instance, that the cavalier of the Syrian coast, Oxypoda cursor (Fabricius), is named from the rapidity with which it traverses great distances.

Many systems have been proposed by different writers for the arrangement of the Crustacea. That proposed by Mr. Milne Edwards recommends itself, being founded on anatomical examination and actual experiment made by himself and M. Audouin. He divides them into two great divisions: I. Those in which the mouth is furnished with a certain number of organs adapted for the prehension or division of food. II. Those in which the mouth is surrounded by ambulatory extremities, the bases of which perform the part of jaws. The first includes the Maxilosa or Mandibulata, again divided into Decapoda, having branchiæ attached to the sides of the thorax, and enclosed in special cavities. The Decapoda are divided into: 1. Brachyura, namely, the Crabs. Cancer, Porlunus, Grapsus, Ocypode, and Doippe, belong to this group. 2. Anomoura, including Droma, Pagurus, Porcellana, and Hippa. 3. Macroura, including the Lobsters, Astacus, Palæmon, the Craw-fish, Palinurus.

Stomatopoda, with external branchiæ, sometimes rudimentary, sometimes none. Thoracic extremities prehensile, or for swimming generally, six or eight pairs. This division includes Mysids, Phyllosoma, Squilla, &c.

The Cirripedia, or barnacles, are a very important division of Crustacea; they are found in all seas, and attach themselves to almost every object in the sea; from the immovable rock to the moving animal; from the little Tunicata to the great turtle, or the whale.

The goose barnacles, Anatifa, have a flexible peduncle. The Balanoidea, or sea acorns, like oysters, are rooted to the spot on which they rest in their infant days; without the power, like the goose barnacle, of swaying to and fro like a pendulum, be their resting-place what it may.

One of the most remarkable animals of this class of Crustacea is the Limulus Moluccanus—the Molucca crab. They are distinguished by a long serrated spine, which looks most formidable. They are in great request in the markets of Java. Linnæus thought that the fossil trilobites were closely allied to the Limulus. Latreille, on the contrary, classed them near the mollusc, chiton. The tail of Limulus so strikingly resembles that of many Trilobites, that the most common observers may perceive an affinity.

Crabs and Craw-fish.

Crabs and lobsters may be regarded as the chiefs or lords of the Crustacean tribes. The crabs have very large claws and smooth backs; the last have small claws and the back covered with spines. Tiberius Cæsar had the face of a poor fisherman scratched by the rugged shell of a craw-fish.

Lobsters, especially, have an amazing fecundity, and yield an immense number of eggs, each female producing from 12,000 to 20,000 in the season. The crab is also very prolific. These eggs are, in the lobster, arranged in packets, which are attached to the lower surface of the tail, to which they are connected by a viscous substance. The manner in which the female lobster disposes of her burden is curious and interesting. Whether she bends or stands erect she is able to hold it obscurely or expose it to the light. Sometimes, according to Coste, the eggs are left immovable, or simply submerged; at others they are subjected to successive washings by gently agitating the false claw which shelters them from right to left. When first exuded from the ovary the eggs are very small, but they seem to increase during the time they are borne about under the tail, and before they are committed to the sand or water they have attained the size of small shot. The evolution of the germ is in progress during six months. At the moment of exclusion the female extends the tail, impresses upon the eggs an oscillating motion, in order to destroy the shell and scatter the larvæ, delivering herself in two or three days of her entire burden (Coste). "As the young lie enclosed within the membrane of the egg," says Couch, "the claws are folded on each other, and the tail is flexed on them as far as the margin of the shield. The dorsal spine is bent backwards, and lies in contact with the dorsal shield, for the young when it escapes from the egg is quite soft; but it rapidly hardens and solidifies by the deposition of calcareous matter on what may be called its skin."