CHAPTER XVI.

CEPHALOPODOUS MOLLUSCA.

"Monstrum horrendum, informe, ingens." VIRGIL.

The highest class of Molluscs is the Cephalopoda, which has been divided by Professor Owen into two Orders, _Tetrabranchiata_, or animals having four branchiæ, and the _Dibranchiata_, having two branchiæ. The first Family of the _Tetrabranchiata_, having the Ammonitidæ, contains the fossil Turrilites and Ammonites. The second Family, _Orthoceratidæ_, contains the fossil Gomphoceras and Orthoceras. The third Family, _Nautilidæ_, contains Nautilus.

The name Cephalopoda, as already stated, is taken from the position of the feet, which are inserted in the anterior part of the head: in Greek κεφαλὴ, _head_, and ποῦς-ποδὸς, _foot_.

The Cephalopodous Molluscs are indeed highly organised for Molluscs, for they possess in a high degree the sense of sight, hearing, and touch. They appear with the earlier animals which present themselves on the earth, and they are numerous even now, although they are far from playing the important part assigned to them in the early ages of organic life upon our planet. The _Ammonites_ and _Belemnites_ existed by thousands among the beings which peopled the seas during the secondary epoch in the history of the globe.

This great class is otherwise divided into two orders: _Tentaculiferous Cephalopods_, those furnished with strong fleshy tentacula, and _Acetabuliferous_, or sucker-bearing.

TENTACULIFEROUS CEPHALOPODS.

In place of bearing simple suckers (_Acetabula_), like the last order of Cephalopods, this group is furnished with true organs of prehension, or tentacles. They differ from the first group chiefly in their more numerous arms, which are quite tentaculiferous, having neither suckers nor capsules, and by having an external shell. The number of living species is extremely limited; for this group of animals belongs peculiarly to the earlier ages of our globe, is gradually becoming extinct, and presents in our days only some rarer species, when we compare them with the prodigious numbers of these beings which animated the seas of the ancient world. In fact, the only living type of the order is the nautilus, which has a singular resemblance in form to the argonaut.

The shell of this mollusc has a regularly convoluted form, the last whorl being equal to all the others. It is divided internally into numerous cells, formed by transverse partitions, concave in front and perforated towards the centre, and forming a kind of funnel, which gives passage to a respiratory siphon.

In the last cell of the shell (Fig. 312) is the animal, covered by its mantle, which covers the walls of the cells. When it contracts itself it is protected by a sort of triangular and fleshy hood. Numerous contractile tentacles, re-entering into the sheath, some of them furnished with numerous lamellæ, surround the head, which is, besides, scarcely distinguished from the body. The head bears two great projecting eyes, planted upon a peduncle.

Like Sepia and Octopus, the mouth of the Nautilidæ is armed with mandibles, fashioned like the parrot's beak; the branchiæ are four in number. The circulating system consists of a ventricle and auricle, and the locomotive tube is protected in its whole length. The shell is secreted by the outer edge of the mantle, while its posterior extremity fashions the walls of the cells, which indicate the successive growth of the individual.

The siphon, which traverses all the chambers, receives and protects the ligament, by the aid of which the Cephalopod is retained in the last chamber of the shell.

Fig. 313 is the same section, with the last cell empty, and with the perforations through which the siphon passes.

The Nautilidæ are inhabitants of the Indian Ocean and the sea round the Molucca Islands. In swimming, their head and tentacles are projected from out of the shell. In walking on rocks they drag themselves along the ground, the body upwards, the head and tentacles beneath. They betake themselves frequently to miry cavities frequented by fish. It is a much more common occurrence to find the empty than inhabited shells of the Nautilus at sea. This, probably, arises from its exposure to the attacks of crustaceans and other marine carnivora. This seems to be proved by the mangled appearance of the edges in the empty shells thus met with.

The Pearly Nautilus, _Nautilus pompilius_ (Fig. 314), is so common on the Nicobar coast that the inhabitants salt and dry its flesh, and store them as provisions. Its shell attains about eight inches in its greatest height. This shell is still used by the Hindoo priests as their conch or shell, with which they summon their devotees to worship. It is nearly round, smooth, transversely blazed in its posterior part, and entirely white anteriorly. A very fine nacre is yielded by this mollusc, which is much used in ornamental cabinet-work. The Orientals make drinking-cups, on which they engrave designs and figures, which form graceful objects. Similar vases were formerly shaped in Europe, which found their way into great houses. In our days they are generally consigned to cabinets of curiosities and the shops of dealers in articles of virtù.

Owen's second order, _Dibranchiata_, contains six families; the first is _Spirulidæ_, containing the curious Spirula, that little gem amongst oceanic shells. The second family is _Sepiadæ_, containing Belemnosis and Sepia. The third is _Belemnitidæ_; the fourth, _Teuthidæ_; the fifth, _Octopodidæ_; and the sixth, _Argonautidæ_.

ACETABULIFEROUS CEPHALOPODA.

To this group belong the cuttle-fish, squids, and argonauts, among existing species, and the Belemnites among the fossil species. Some of these creatures are large, and essentially flesh-eaters, or carnivorous; and, if we may believe all that has been written respecting them, very formidable ones. Listen to Michelet, while he paints the warlike humour of these inhabitants of the deep:--"The Medusæ and Molluscs," says this popular author, "are generally innocent creatures, and I have lived with them in a world of gentle peace. Few flesh-eaters among them; those even which are so, only kill to satisfy their wants, living for the most part on life just commenced--on gelatinous animals, which can scarcely be called organic. From this world grief was absent. No cruelty and no passion. Their little souls, if mild, were not without their ray of aspiration towards the light, and towards what comes to us from heaven, and towards that love, revelling in that changing flame which at night is the light of the deep. It is now, however, necessary to describe a much graver world: a world of rapine and of murder; from the very beginning, from the first appearance of life, violent death appeared; sudden refinement, useful but cruel, purification, of all which has languished, or which may linger or languish, of the slow and feeble creation whose fecundity had encumbered the globe.

"In the more ancient formations of the old world we find two murderers--a nipper and a sucker. The first is revealed to us by the imprint of the trilobite, an order now lost, the most destructive of extinct beings. The second subsists in one gigantic fragment, a beak nearly two feet in length, which was that of a great sucker or cuttle-fish (_Sepia_). If we may judge from such a beak, this monster, if the other parts of the body are in proportion, must have been enormous; its ventose, invincible arms, of perhaps twenty or thirty feet, like those of some monstrous spider. The sucker of the world, soft and gelatinous! it is himself. In making war on the molluscs he remains mollusc also; that is to say, always an embryo. He presents the strange, almost ridiculous, if it was not also terrible, appearance of an embryo going to war; of a foetus furious and cruel, soft and transparent, but tenacious, breathing with a murderous breath, for it is not for food alone that it makes war: it has the wish to destroy. Satiated, and even bursting, it still destroys. Without defensive armour, under its threatening murmurs there is no peace; its safety is to attack. It regards all creatures as a possible enemy. It throws about its long arms, or rather thongs, armed with suckers, at random." Such is the somewhat exaggerated picture which the eloquent historian and poet draws of the Molluscous Cephalopod, and it must be admitted that there is a basis of truth in this, as well as in the more recent one painted by Victor Hugo, in his eloquent book, "Les Travailleurs de la Mer." Where, however, there is so much of the fictitious floating about, it will be our endeavour to eliminate facts only.

FAMILY OF THE SEPIADÆ.

The body of the cuttle-fish (_Sepia_) is thus a very singular structure, somewhat reminding us of certain species of polyps. We find a body or abdominal mass, hand ahead, separated by compression, sufficiently marked. The body is covered by the mantle, which has the form of a sac opened only in front by a transverse cleft. The head has a projecting and well-developed eye on each side; it is surmounted by a sort of fleshy funnel, which is divided by four pairs of tentacles. At the bottom of this tentacular funnel is the mouth; and from the anterior opening in the mantle a tube issues, which is wide at its base.

The Sepiadæ have eight arms rising from the crown of the head armed with four rows of suckers, two long slender tentacles with broadly-expanding ends, and stalked suckers; eyes moving in their sockets, and body broadly ovate in Sepia.

If we study the general aspect of the animal more closely, we find that the tentacles--which serve at once as organs of locomotion for swimming, for creeping, and as prehensile organs for seizing and retaining its prey--are conical, very long, and all of the same form. Each of them has towards its axis a longitudinal canal, which encloses a great nerve, which is also surrounded with muscular fibres, arranged in rays. The suckers, already described, occupy all the internal surface of the eight tentacular arms, which are arranged in two rows, having the form very nearly of a semi-spherical capsule. Of these suckers, each arm of the cuttle-fish carries about two hundred and forty, the total number being nearly a thousand. The mouth we have already described, in Dr. Roget's words: "The teeth move vertically, much as the cutting edge of the two blades of a pair of scissors move upon each other, tearing the prey by the assistance of their hooked terminations."

The tongue is covered on its upper part by a thick horny bed, bristling in the centre with a series of recurving teeth, while its edge is armed with three other erect teeth, which are slender and hooked. The oesophagus is long and slender. At the abdomen the gullet expands into a sort of frill, to which succeeds a gizzard, with strong fleshy walls; and, finally, a very short intestine, which directs itself forward, terminating on the median line of the body. Towards the anterior parts is a cavity, of which a few words must be said. It occupies the free space comprised between the exterior surface of the abdomen and the internal face of the mantle; and here the respiratory organs, namely, the _branchiæ_, are lodged. Here, also, are the reproductive and excretory organs.

The branchiæ, which are two in number, are voluminous, but short, tufted, and leaf-like. The branchial cavity can dilate and contract itself alternately. It communicates externally by two openings: the one, fashioned into a cleft, receives, while the other, which is prolonged into a tube, serves to eject, the water, and becomes a powerful organ of locomotion.

The inspiration of the animal is thus made by a cleft in the mantle, and expiration by the tube: the renewal of the respirable liquid acts as a sort of sucking and forcing pump, at the surface of the lamellar branchials. The cuttle-fish, in short, will be at no loss to reply to the question of the Don Diego of Corneille--

"Rodrique, as-tu du cœur?"

for they have three hearts. The two first are placed at the end of the branchiæ. With each beat of the pulse the venous blood is brought from all parts of the body, and propelled through each gill or branchiæ. Vivified by respiration in the internal tissue of the branchiæ, it is carried by the veins into the third heart, situated upon the median line of the body; and now the regenerated fluid is again distributed throughout the rest of the economy.

Not to oppress the reader with anatomical details, we shall just remark that the gaze of the cuttle-fish is decided and threatening. Its projecting eyes and golden-coloured iris are said to have something of fascination in them. The animal seems able even to economise the power of its glance, being able to cover its eyes from time to time by contracting the skin which surrounds them, and bringing the two translucent eyelids with which it is furnished closer together.

The cuttle-fishes are essentially aquatic and marine animals. We find them in every sea in all parts of the world; but they are most formidable in warm countries. They have a great predilection for the shore. During their youth they associate in flocks; but with age they fly from association, and retire into the clefts and hollows of the rocks. The old cuttle-fish is only found in rugged and rocky places, bristling with naked, pointed rocks, which have been worn by the waves, but generally in places only a few feet below the level of low water. "How often," says D'Orbigny, "have we not observed the cuttle-fish in his favourite retirement! There, with one of his arms cramped to the walls of its dwelling, it extends the other towards the animals which pass at its gate, embraces them, and by its power renders useless all their efforts to disengage themselves."

If we observe a cuttle-fish when it is what may be called walking, either on land or at the bottom of the sea, it will be seen to walk on one side, its head downwards, its mouth touching the ground, the arms extended and grappling some supporting object, and drawing the body forward; at the same time the arms at the opposite side are contracted and folded up, so as to assist by a contrary movement. On shore the movement of these animals is very slow. On the other hand, they swim very rapidly, assisted by all their arms, and aided by the water ejected from the locomotive tube, their movement being most frequently backwards, the body first, the six superior arms placed horizontally, the two others brought together above: the first help to sustain them in their horizontal position, the last to guide them, inclining to the right or left as the animal changes its direction.

The cuttle-fishes feed on crustaceans, fishes, and also on shelled molluscs--every kind of animal, in fact, which comes within their reach; so that it is readily taken by means of the flesh of fish or crustaceans, in which a strong hook is concealed. They live for five or six years, and reproduce by eggs, which are large, and generally found in clusters, known to fishermen under the name of _sea-grapes_.

Like the zoophytes, they possess the property of redintegration, already described, being able to reproduce any arm that may be destroyed. There is another singular peculiarity which the cuttle-fish shares with man. Under the influence of strong emotion the human face becomes pale, or blushes, and in some individuals it is said to become blue. This has always been supposed to be an attribute of humanity; but the cuttle-fish shares it with our race. Yielding to the impressions of the moment, the cuttle-fish suddenly changes colour, and, passing through various tints, it only resumes its familiar one when the cause of the change has disappeared. They are, in fact, gifted with great sensibility, which reacts immediately upon their tissues, these being extremely elastic and delicate. Sudden changes of colour are produced--changes which far exceed the same phenomena in man. Under the influence of passion or emotion man is born to blush, but under no sort of excitement does he cover himself with pustules; this the cuttle-fish does: it not only changes colour, but it covers itself with little warts. "Observe a cuttle in a pool of water," says D'Orbigny, "as it walks round its retreat--it is smooth, and of very pale colour. Attempt to seize it, and it quickly assumes a deeper tint, and its body becomes covered on the instant with warts and hairs, which remain there until its confidence is entirely restored."

The following fact is abbreviated from the "Natural History and Fishery of the Sperm Whale." Mr. Beale had been searching for shells among the rocks in Bonin Island, and was much astonished to see at his feet a most extraordinary-looking animal, crawling back towards the surf which it had just left. It was creeping on its eight legs, which, from their soft and flexible nature, bent considerably under the weight of its body, so that it was just lifted by an effort above the rocks. It appeared much alarmed, and made every attempt to escape. Mr. Beale endeavoured to stop it by putting his foot on one of its tentacles, but it liberated itself several times in spite of all his efforts. He then laid hold of one of the tentacles with his hand, and held it firmly, and the limb appeared as if it would be torn asunder in the struggle. To terminate the contest, he gave it a powerful jerk; it resisted the effort successfully, but the moment after the enraged animal lifted a head with large projecting eyes, and loosing its hold of the rocks, suddenly sprang upon Mr. Beale's arm, which had been previously bared to the shoulder, and clung to it with its suckers, while it endeavoured to get the beak, which he could now see, between the tentacles, in a position to bite him. Mr. Beale describes its cold slimy grasp as extremely sickening, and he loudly called to the captain, who was also searching for shells, to come to his assistance. They hastened to the boat, and he was released by killing his tormentor with a boat-knife, when the arms were disengaged bit by bit. Mr. Beale states that this Cephalopod must have measured across its expanded arms about four feet, while its body was not bigger than a large hand clenched. It was the species called the rock-squid by whalers.

These formidable and curious Cephalopods, the Μαλάκια of Aristotle, _Mollia_ of Pliny, and _Cephalophora_ of De Blainville, have the mantle, according to Cuvier, united beneath the body, thus forming a muscular sac which envelopes the whole viscera. The body is soft and fleshy, varying much in form, being sub-spherical, sub-elliptical, and cylindrical, the sides of the mantle in many species extending into fleshy fins. The head protrudes from the muscular sac, and is distinct from the body; it is gifted with all the usual senses, the eyes in particular, which are either pedunculate or sessile, being large and well developed. The mouth is anterior and terminal, armed with a pair of horny or calcareous mandibles, which bear a strong resemblance to the bill of a parrot, acting transversely, one upon the other. Its position is the bottom of a sub-conical cavity, forming the base of numerous fleshy tentacular appendages which surround it, and which are termed arms by some writers. These appendages in the great majority of living species are provided with suckers, _acetabula_ (cupping-glass-like appendages), by means of which the animal moves at the bottom of the sea, head downwards, or attaches itself to its prey. These suckers are armed or unarmed with a long, sharp, horny claw. In the unarmed acetabulum, the mechanism for adhesion is well described by Dr. Roget: "The circumference of the disk," says this writer, "is raised by a soft and turned margin; a series of long slender folds of membrane covering corresponding fascicula of muscular fibre converge from the circumference towards the centre of the sucker, at a short distance from which they leave a circular aperture; this opens into a cavity which widens as it descends, and contains a cone of soft substance rising from the bottom of the cavity, like the piston of a syringe. When the sucker is applied to the surface, for the purpose of adhesion, the piston, having previously been raised so as to fill the cavity, is retracted, and a vacuum produced, which may be still further increased by the retraction of the plicated portion of the disk." Here we have an excellent description of the apparatus for holding on. When the animal is disposed to let go his hold, according to Professor Owen, "the muscular arrangement enables the animal to push forward the piston, and thus in a moment destroy the vacuum which retraction had produced."

In the case of the armed Cephalopods (_Onychoteuthis_), Professor Owen remarks, "that there are circumstances in which even the remarkable apparatus described by Dr. Roget would be insufficient to fulfil the offices in the economy of Nature for which the Cephalopod was created, and that in species which have to contend with the agile mucous-clad fishes more powerful organs of prehension are superadded to the suckers, so that in the calamary the base of the piston is, he remarks, enclosed in a horny hoop, the outer and anterior margin of which is developed into a series of sharp curved teeth, which can be firmly pressed into the flesh of a struggling prey by the contraction of the surrounding transverse fibres, and can be withdrawn by the action of the retracting fibres of the piston. "Let the reader," the professor adds, "picture to himself the projecting weapon of the horny hoop developed into a long, curved, sharp-pointed claw, and these weapons clustered at the expanded terminations of the tentacles, and arranged in a double alternate series along the internal surface of the eight muscular feet, and he will have some idea of the formidable nature of the carnivorous cephalopod." The professor notices another structure which adds greatly to the prehensile powers of the uncinated Cephalopods. "At the extremities of the long tentacles a cluster of small, simple, unarmed suckers may be observed at the base of the expanded part. When these latter suckers are applied to one another, the tentacles are firmly locked together at that part, and the united strength of both the elongated peduncles can be applied to drag towards the mouth any resisting object which has been grappled by the terminal hooks. There is no mechanical contrivance which surpasses this structure; art has remotely imitated it in the fabrication of the obstetrical forceps, in which either blade can be used separately, or, by the interlocking of a temporary blade, be made to act in combination."--_Cyc. of Anat._

The third Family, _Belemnitidæ_, contains Belemnitella and Belemnites, and other genera of less importance; they are all now extinct, although once numerous as species.

The cuttles, _Sepia_ (Fig. 315), have the body fleshy and depressed, continued into a sac, and bordered on all its length on both sides with a wing or narrow fin, the larger short and flat, broader than it is long, with two large eyes, covered by an expansion of the skin, which becomes transparent over a surface equal to the diameter of the iris, and furnished with inferior contractile eyelids.

This head is surmounted by ten tentacular arms or feet, eight of which are short and conical, and two long and slender, terminating in a sort of spatula. These arms are all armed with suckers, and are perfectly retractile. They surround a mouth armed with two horny jaws not unlike the beak of a parrot.

The skin of the cuttle-fish presents in one vast hollow, occupying all the extent of the back, a great calcareous part, the form and structure of which is quite characteristic of this genus. It is known as the cuttle-bone (Fig. 316). This bone is used for many purposes; among others, it is used in a powdered state as a dentifrice. It is sometimes suspended in the cage with captive birds, that they may whet their beaks on it, and collect phosphate of lime for the formation and repair of their bones. The osselet is oval or oblong, some provided with a slightly salient point. The upper part is surrounded with a horny or cretaceous margin, and presents in the centre a combination of spongy cells.

Most of the Cephalopods secrete a blackish, inky fluid, to which some allusion has been made, but the uses of which, in the economy of the animals, is imperfectly known. The cuttles have considerable quantities of this liquor, which is contained in a sort of sac or ink-purse, placed low down in the abdomen. When the animal is pursued or threatened with danger it discharges a jet of the fluid, which renders the water thick and muddy, and permits it to escape in the obscurity from its pursuers. It appears that the cuttle-fish avails itself of this stratagem when left accidentally ashore. It is related of an English officer, that, having dressed for dinner, and having some time to spare, he proceeded along the shore on his favourite search for objects of natural history. He reached a hollow rock in which a cuttle-fish had established its quarters; he soon detected the animal, which looked at him for some time with its great prominent eyes; in short, they watched each other with fixed attention. This mute contemplation came to a sudden and unexpected termination by the discharge of a voluminous jet of inky fluid, which covered the officer, which was the more unfortunate, since he was in his summer dress of white trousers.

The ink of the cuttle-fish is a favourite pigment, used in water-colour painting under the name of _sepia_. It is truly indestructible; and the hard and black substance found in the sac of fossil species of cuttle-fish when diluted with water produces a brilliant sepia. This property of the inky fluid was well known to the Romans, who used it in making ink. It was long supposed to be the chief ingredient in China ink; but a recent traveller, Mr. Seebold, who has visited the manufactory, and investigated the subject, has revealed the true process by which it is prepared.

The cuttle-fish affects the sea-shore; they are along-shore molluscs. The flattened form of their bodies is favourable to a coasting life, by permitting them to rest easily on the bottom. Still they do not remain all the year round upon the coast. The cold in temperate regions, and the opposite reason in warm regions, leads them to withdraw from the shore, to which they only return in the spring. They are rarely seen in the Channel in winter, but with the vernal sun they appear in large shoals. What is the mechanism by which these animals are moved? When the cuttle-fish wishes to swim rapidly and backwards, they advance in the water by means of the locomotive tube, sending back the ambient liquid. When they wish to approach a prey slowly in order to seize it, they swim by the aid of their fins and arms. In order to swim backwards, they contract the arms provided with tentacles, and spread out horizontally the arms without tentacles.

The cuttles are flesh-eaters, and tolerably voracious. They feed themselves upon fishes, molluscs, and crustaceans. They are true aquatic brigands, who kill not to feed themselves, but for the sake of killing; and Nature, by a just equilibrium, applies to them the _lex talionis_. They fall victims, in their turn, to the vengeful jaws of the porpoises and dolphins. Such is the terrible law of Nature: some must die that others may live. Michelet gives us a glimpse of the manner in which the dolphins dispose of the cuttle-fish in his "Livre de la Mer." "These lords of the ocean," he says, "are so delicate in their tastes that they eat only the head and arms, which are both tender and of easy digestion. They reject the hard parts, and especially the after-part of the body. The coast at Royan, for example, is covered with thousands of these mutilated cuttle-fish. The porpoises take most incredible bounds, at first to frighten them, and afterwards to run them down; in short, after their feast, they give themselves up to gymnastics."

In the spring the cuttle-fishes deposit their eggs, but without abandoning them. On the contrary, they exhibit a truly maternal care, taking much trouble to attach them to some submarine body, in which position the temperature of the water serves to hatch the eggs. _Sepia officinalis_, for example, chooses, at the moment of laying, a stem of _Fucus_, a foot of _Gorgonia_, or some other solid submarine body not less in dimensions than the little finger, and there it firmly attaches its eggs, which are pear-shaped, that is, pointed at one extremity, while a long _lanière_ of a gelatinous nature, flat and black in appearance, with which they are provided, surrounds the solid body like a ring. Each female lays and attaches in this manner from twenty to thirty eggs, which are clustered together somewhat like a bunch of fine black grapes (Fig. 318). About a month after this the eggs are hatched.

The colours of _Sepia officinalis_ vary considerably; but in general it may be remarked that the males are ornamented with deeper colours than the females. Transverse bands of a blackish brown furrow their backs, and diminish their breadth. Outside of these bands are small spots of a vivid white: very near the edge there is a white border, accompanied inside with a second edging of a beautiful violet. The median and anterior parts of the body are spotted here and there; beneath, a whitish tint with reddish speckles prevails.

The cuttle-fishes are found on every shore, and wherever they are found they are eaten, for their flesh is savoury. They are usually fried or boiled. They form an excellent bait for large ground-fish, such as dog-fish, rays, and congers, which are fond of their flesh.

Thirty species are known, and they are chiefly characterised by the arrangement and form of the cupules of the arms. _Sepia officinalis_ is common on the shores of the ocean from Sweden to the Canaries, and in all parts of the Mediterranean.

The fourth family, _Teuthidæ_, contains _Loligopsis_, _Cranchia_, and _Loligo_.

The _Calmars_ were described by Aristotle under the name of Γείφις, and by Pliny under that of _Loligo_, which is still retained as the generic name. Their popular name of Calmar (calamar in old French) is taken from their resemblance to certain species of ink-holders. Oppian, who endowed the argonaut with wings, believed that the calmar also could take to the air, in order to avoid his enemies. Nevertheless, he was much puzzled how to give the form and functions of a bird to a fish. Themistocles, by way of insult to the Eretrians, likened them to calmars, saying they had swords and no hearts. Athenæus, a Greek physician before Galen, dwelt upon the nourishing properties of the flesh of the calmar.

Common enough in temperate regions, the calmars abound in the seas of the Torrid zone: they are gregarious, and live in numerous shoals, their bands taking every year the same direction, their emigration proceeding from temperate to warm regions--nearly the same course as that followed by the herrings and pilchards.

The calmars, like the cuttles, propel themselves backwards through the water with great velocity, driving back the water by means of their locomotive tube, moving with such vigour and promptitude that they have been known to throw themselves out of the water, falling on the shore or on the deck of a vessel. They only appear momentarily on the shore, and only sojourn there to deposit their eggs, which are gelatinous in substance, about the level of the lowest tides. The body in the calmars is longer than in the cuttle-fish, cylindrical in shape, and terminating in a point, having two lateral fins, which occupy the lower half or third of its body.

In the common calmar, _Loligo vulgaris_ (Fig. 319), and the _Loligo_ _Gahi_ (Fig. 320), we have two extreme forms represented, both taken from the magnificent work of MM. D'Orbigny and Ferussac, on the _Cephalopodes acetabulifores_. These molluscs are whitish-blue and transparent, covered with spots of bright red. The osselet is lanceolate--that of the male elongated and somewhat resembling a feather, that of the female much broader and more obtuse. Their head is short, furnished with two large projecting eyes; the mouth is surrounded with ten arms, provided with suckers, two of these being much longer than the others, having peduncles or foot-stalks.

The internal bone of the calmar differs much from that of the cuttles; it is thin, horny, transparent, and somewhat resembling a feather, from a portion of which the _barbs_ have been removed. Their food consists chiefly of small fishes and molluscs. With the greater fishes and cetaceæ they carry on constant war. They are caught and used for various purposes; along the coast they are eaten; the fishermen use them as bait, especially in fishing for cod.

It is no easy task to separate the real from the fabulous history of the Cephalopods. Aristotle and Pliny have alike assisted, by their marvellous relations, to throw that halo of wonder round it which the light of modern science has not altogether dispelled. Pliny the Ancient relates the history of an enormous cuttle-fish which haunted the coast of Spain, and destroyed the fishing-grounds. He adds that this gigantic creature was finally taken, that its body weighed seven hundred pounds, and that its arms were ten yards in length. Its head came by right to Lucullus, to whose gastronomical privileges be all honour. It was so large, says Pliny, that it filled fifteen amphoræ, and weighed seven hundred pounds also.

Some naturalists of the Renaissance, such as Olaüs Magnus and Denis de Montfort, gave credit--which they are scarcely justified in doing--to the assertions of certain writers of the north of Europe, who believed seriously in the existence of a sea-monster of prodigious size which haunted the northern seas. This monster has received the name of the _Kraken_. The Kraken was long the terror of these seas; it arrested ships in spite of the action of the wind, sails, and oars, often causing them to founder at sea, while the cause of shipwreck remained unsuspected. Denis de Montfort gives a description and representation of this Kraken, which he calls the Colossal Poulpe, in which the creature is made to embrace a three-masted ship in its vast arms. Delighted with the success which his representation met with, Denis laughed at the credulity of his contemporaries. "If my Kraken takes with them," he said, "I shall make it extend its arms to both shores of the Straits of Gibraltar." To another learned friend he said, "If my entangled ship is accepted, I shall make my Poulpe overthrow a whole fleet."

Among those who admitted the facetious history of the Kraken without a smile, there was at least one holy bishop, who was, moreover, something of a naturalist. Pontoppidan, Bishop of Bergen, in Norway, in one of his books assures us that a whole regiment of soldiers could easily manœuvre on the back of the Kraken, which he compares to a floating island. "Similior insulæ quan bestiæ," wrote the good Bishop of Bergen.

In the first edition of his "System of Nature," Linnæus himself admits the existence of this colossus of the seas, which he calls _Sepias microcosmos_. Better informed in the following edition, he erased the Kraken from his catalogue.

The statements of Pliny respecting the Colossal Poulpe, like those of Montfort about the Kraken, are evidently fabulous. It is, however, an undisputed fact that there exists in the Mediterranean and other seas cuttle-fish--a congenerous animal--of considerable size. A calmar has been caught in our own time, near Nice, which weighed upwards of thirty pounds. In the same neighbourhood some fishermen caught, twenty years ago, an individual of the same genus nearly six feet long, which is preserved in the Museum of Natural History at Montpellier. Péron, the naturalist, met in the Australian seas a cuttle-fish nearly eight feet long. The travellers Quoy and Gaimard picked up in the Atlantic Ocean, near the Equator, the skeleton of a monstrous mollusc, which, according to their calculations, must have weighed two hundred pounds. M. Rung met, in the middle of the ocean, a mollusc with short arms, and of a reddish colour, the body of which, according to this naturalist, was as large as a tun cask. One of the mandibles of this creature, still preserved in the Museum of the College of Surgeons, is larger than a hand.

In 1853 a gigantic cephalopod was stranded on the coast of Jutland. The body of this monster, which was dismembered by the fishermen, furnished many wheelbarrow loads, its pharynx, or back part of the mouth, alone being as large as the head of an infant. Dr. Steenstrup, of Copenhagen, who published a description of this creature under the name of _Architeuthis dux_, shows a portion of the arm of another cephalopod, which is as large as the thigh-bone of a man. But a well-authenticated fact connected with these gigantic cephalopods is related by Lieutenant Bayer, of the French corvette Alecton, and M. Sabin Berthelot, French Consul at the Canary Islands, by whom the report is made to the Académie des Sciences.

The steam-corvette Alecton was between Teneriffe and Madeira when she fell in with a gigantic calamary, not less--according to the account--than fifteen mètres (fifty feet) long, without reckoning its eight formidable arms, covered with suckers, and about twenty feet in circumference at its largest part, the head terminating in many arms of enormous size, the other extremity terminating in two fleshy lobes or fins of great size, the weight of the whole being estimated at four thousand pounds; the flesh was soft, glutinous, and of reddish-brick colour.

The commandant, wishing in the interests of science to secure the monster, actually engaged it in battle. Numerous shots were aimed at it, but the balls traversed its flaccid and glutinous mass without causing it any vital injury. But after one of these attacks the waves were observed to be covered with foam and blood, and, singular thing, a strong odour of musk was inhaled by the spectators. This musk odour we have already noticed as being peculiar to many of the Cephalopods.

The musket-shots not having produced the desired results, harpoons were employed, but they took no hold on the soft impalpable flesh of the marine monster. When it escaped from the harpoon it dived under the ship, and came up again at the other side. They succeeded at last in getting the harpoon to bite, and in passing a bowling hitch round the posterior part of the animal. But when they attempted to hoist it out of the water the rope penetrated deeply into the flesh, and separated it into two parts, the head with the arms and tentacles dropping into the sea and making off, while the fins and posterior parts were brought on board: they weighed about forty pounds.

The crew were eager to pursue, and would have launched a boat, but the commander refused, fearing that the animal might capsize it. The object was not, in his opinion, one in which he could risk the lives of his crew. PL. XXIV. is copied from M. Berthelot's coloured representation of this scene. "It is probable," M. Moquin-Tandon remarks, commenting on M. Berthelot's recital, "that this colossal mollusc was sick or exhausted by some recent struggle with some other monster of the deep, which would account for its having quitted its native rocks in the depths of the ocean. Otherwise it would have been more active in its movements, or it would have obscured the waves with the inky liquid which all the Cephalopods have at command. Judging from its size, it would carry at least a barrel of this black liquid, if it had not been exhausted in some recent struggle."

"Is this mollusc a calmar?" asks the same writer. "If we might judge from the figure drawn by one of the officers of the Alecton during the struggle, and communicated by M. Berthelot, the animal had terminal fins, like the calmars; but it has eight equal arms, like the cuttle-fish. Now the calmars have ten, two of them being very long. Was this some intermediate species between the two? Or must we admit, with MM. Crosse and Fisher, that the animal had lost its more formidable tentacles in some recent combat?"[13]

The fifth family, _Octopodidæ_, contains _Eledone_, _Octopus_, _Pinnoctopus_, _Cirroteuthis_, _Philonexis_, and _Scærgus_.

The _Octopoda_, without tentacles, have eight long arms, united at the base by a web; the suckers in two rows, which are sessile; the eyes fixed; shell, two short stiles enclosed in the mantle; the body united to the head by a broad neck-band; no side-fins; shell internal and rudimentary in the British species; body oval, warty, and without fins, in _Octopus_; small and oblong, arms tapering and webbed, and suckers in a single row, in _Eledone_ (Fig. 321).

In his great work, Professor Owen proposes to divide the Cephalopods into two groups, which he calls _Dibranchiata_, characterised by the presence of two branchiæ, which would bring together all the naked Cephalopods, including Sepia, Loligo, Octopus, Kassia, and Ommastrephos; and _Tetrabranchiata_, having four branchiæ, to which the _Nautilus_, and most of the fossil Cephalopods, such as the _Ammonites_, belong. Most of the first group are represented in the British seas, but the second are altogether absent.

The _Decapoda_ are of all sizes. Dr. Grant describes the body, or mantle, of _Sepiola vulgaris_, found on our coast, as measuring about six lines in length, and as much in breadth, while the head measures four lines in length, and, from the magnitude of the eyes, must be equal in breadth with the body. In _Onychoteuthis_, distinguished for its uncinated suckers, they are found of the size of a man. In Cook's first voyages, the naturalists to the expedition, "Banks and Solander," to quote Professor Owen's account, "found the dead carcase of a gigantic species of this kind floating in the sea between Cape Horn and the Polynesian Islands, in 30° 44' S. lat., and 110° 10' W. long. It was surrounded by sea birds, which were feeding on its remains. From the parts of this specimen which are still preserved in the Hunterian Museum, and which have always strongly excited the attention of naturalists, it must have measured at least six feet from the end of the tail to the end of the tentacles."

In the genus _Eledone_ the arms are reunited at their base by a very short membrane, with only a single row of suckers. The two best-known species of this group inhabit the Mediterranean. The one is _Eledone moschatus_, known in Italy under the name of Muscardino, from the strong odour of musk which it emits, even after death and desiccation; the other is _Eledone cirrhosus_, a small species, bluish-grey on the back, and whitish under the belly.

The habits of _Eledone moschatus_ have been carefully studied by M. Verany. The able naturalist of Nice preserved many of these animals during a month, in a great aquarium, noting their habits. When in a state of tranquillity, the _Eledone_ clung to the sides of the glass tank in which it was kept. Its head is then inclined forwards, with the sac hanging behind; the locomotive tube, turned upwards, presents the orifice between the arms. In this state the animal is yellowish in colour, its eyes dilated, its inspirations regular. But if irritated, a remarkable change takes place: its body assumes a fine maroon colour, and it is covered with numerous tubercles; the eye becomes contracted, a column of water is forcibly ejected from the locomotive tube at the aggressor, and the respiration becomes precipitate, jerky, and irregular. The creature would take a strong inspiration, and, having collected its force, suddenly throw a jet of water to a distance of more than three feet. This state of passion, which the slightest touch is sufficient to produce, endures for half an hour or more. When it ceases, the animal resumes its form and primitive colours; but the least shock impressed on the water is sufficient to give it a deeper tint, which passes like a flash of lightning over the skin of this singular proteus.

The Eledone sleeps by day as well as by night, attaching itself in its sleep to the walls of its prison, leaving its arms to float around, the two inferior ones extending backwards, and the sac inclining over them; its eyes are then contracted, and in part covered by the eyelids. Its respiration is regular and slow, and any ejection of water very rare; its colour is then of a livid grey, and vinous red below, with whitish spots, while the brown spots have now entirely disappeared. While still asleep, it is watchful and attentive to all the dangers which could surprise it. The extremities of the arms floating round its body are ready to announce the approach or contact of any other object. Even the most delicate touch is perceived immediately, and it shrinks from the hand which seeks to approach. Under every circumstance the Eledone exhales a strong odour of musk, which it preserves long after death.

When the Eledone swims, which it rarely does unless pressed by some urgent necessity, it carries the sac in advance, the arms floating behind--the six upper ones being on a horizontal line, the two others approaching each other below. Thus arranged, it presents, in consequence of its flattened form, a very large resisting surface to the water, its progress being due to the alternate dilatation and contraction of the body, which expels the water through the locomotive tube, and by reaction produces a rapid and jerking movement. Sometimes the arms aid the movement; the eyes of the animal are then much dilated, and its colour a clear livid yellow, finely shaded with red, and covered with bright spots.

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:"

"Illi robur et æs triplex Circa pectus erat, qui fragilem truci Commisit pelago ratem Primus...."

_Horace_, I. Car. iii. l. 9.

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.

FOOTNOTES:

[Footnote 13: Is it necessary to say that even this account--apparently so well authenticated, not to speak of the representation drawn on the spot--should be taken "cum grano salis?"--ED.]