THE transition from the ordinary mode of the locomotion of fishes by swimming to that of climbing has been ably illustrated by the Rev. Dr. Buckland, who showed, in a communication to the Ashmolean Society, in 1843, that the fins in certain genera perform the functions of feet and wings. Thus, "fishing-frogs" have the fins converted into feet, or paddles, by means of which they have the power of crawling or hopping on sand and mud; and another species can live three days out of the water, and walk upon dry land. The climbing perch of the Indian rivers is known to live a long time in the air, and to climb up the stems of palm-trees in pursuit of flies, by means of spinous projections on its gill-covers. Fishes of the silurus family have a bony enlargement of the first ray of the pectoral fin, which is also armed with spines; and this is not only an offensive and defensive weapon, but enables the fish to walk along the bottom of the fresh waters which it inhabits. The flying-fishes are notorious examples of the conversion of fins into an organ of movement in the air. M. Deslongchamps has published, in the "Transactions of the LinnÆan Society of Normandy," 1842, a curious account of the movements of the gurnard at the bottom of the sea. In 1839, he observed these movements in one of the artificial fishing-ponds, or fishing-traps, surrounded by nets, on the shore of Normandy. He saw a score of gurnards closing their fins against their sides, like the wing of a fly in repose, and without any movement of their tails, walking along the bottom by means of six free rays, three on each pectoral fin, which they placed successively on the ground. They moved rapidly forwards, backwards, to the right and left, groping in all directions with these rays, as if in search of small crabs. Their great heads and bodies seemed to throw hardly any weight on the slender rays, or feet, being suspended in water, and having their weight further diminished by their swimming-bladder. During these movements the gurnards resembled insects moving along the sand. When M. Deslongchamps moved in the water, the fish swam away rapidly to the extremity of the pond; when he stood still, they resumed their ambulatory movement, and came between his legs. On dissection, we find these three anterior rays of the pectoral fins to be supported each with strong muscular apparatus to direct their movements, apart from the muscles that are connected with the smaller rays of the pectoral fin.

Dr. Buckland states that Miss Potts, of Chester, had sent to him a flagstone from a coalshaft at Mostyn, bearing impressions which he supposed to be the trackway of some fish crawling along the bottom by means of the anterior rays of its pectoral fins. There were no indications of feet, but only scratches, symmetrically disposed on each side of a space that may have been covered by the body of the fish whilst making progress, by pressing its fin-bones on the bottom. As yet, no footsteps of reptiles, or of any animals more highly organized than fishes, have been found in strata older than those which belong to the new red sandstone. The abundant remains of fossil fishes, armed with strong bony spines, and of other fishes allied to the gurnard, in strata of the carboniferous and old red sandstone series, would lead us to expect the frequent occurrence of impressions made by their locomotive organs on the bottoms of the ancient waters in which they lived. Dr. Buckland proposed to designate these petrified traces or trackways of ancient fishes by the term of fish-tracks.

Crabs and Lobsters are strange creatures: strange in their configurations; strange in the transmutations which they exhibit from the egg to maturity; strange in the process they undergo of casting off, not only their shell, but the covering of their eyes, of their long horns, and even the lining of their tooth-furnished stomach; strange, also, are they in their manners and habits. Many a reader, in wandering along the sea-shore, may have disturbed little colonies of Crabs quietly nestling in fancied security amidst banks of slimy sea-weed; and in the nooks and recesses of the coast, the shallows, and strips of land left dry at ebb-tide, may be seen numbers of little, or perchance large, Crabs, some concealed in snug lurking-places, others tripping, with a quick side-long movement, over the beach, alarmed by the advance of an unwelcome intruder. Some are exclusively tenants of the water, have feet formed like paddles for swimming, and never venture on land; others seem to love the air and sunshine, and enjoy an excursion, not without hopes of finding an acceptable repast, over the oozy sands; some, equally fond of the shore and shallow water, appropriate to themselves the shells of periwinkles, whelks, &c., and there live in a sort of castle, which they drag about with them on their excursions, changing it for a larger as they increase in measure of growth. They vary in size from microscopic animalcules to the gigantic King Crab: [21] to the former, the luminosity of the ocean, or of the foam before the prows of vessels, is, to a great extent, attributable, each minute creature glowing with phosphoric light.

The Bernhard Crab has been proved to have the power of dissolving shells, it not being unusual to find the long fusiform shells which are inhabited by these animals with the inner lip, and the greater part of the pillar on the inside of the mouth, destroyed, so as to render the aperture much larger than usual. Dr. Gray is quite convinced that these Crabs have the above power, some to a much greater degree than others.

Certain Crabs, especially in the West Indies, are almost exclusively terrestrial, visiting the sea only at given periods, for the deposition of their eggs. These Crabs carry in their gill-chambers sufficient water for the purpose of respiration; they live in burrows, and traverse considerable tracts of land in the performance of their migratory journeys. Of these, some, as the Violet Crab, are exquisite delicacies.

Of a great Crab migration we find these details in the "Jamaica Royal Gazette:"—In 1811 there was a very extraordinary production of Black Crabs in the eastern part of Jamaica. In June or July the whole district of Manchidneed was covered with countless numbers, swarming from the sea to the mountains. Of this the writer was an eye-witness. On ascending Over Hill from the vale of Plantain Garden River, the road appeared of a reddish colour, as if strewed with brick-dust. It was owing to myriads of young Black Crabs, about the size of the nail of a man's finger, moving at a pretty quick pace, direct for the mountains. "I rode along the coast," says the writer, "a distance of about fifteen miles, and found it nearly the same the whole way. Returning the following day, I found the road still covered with them, the same as the day before. How have they been produced, and where do they come from? were questions everybody asked, and nobody could answer. It is well known that Crabs deposit their eggs once a year, in May; but, except on this occasion, though living on the coast, I had never seen above a dozen young Crabs together; and here were myriads. No unusual number of old Crabs had been observed in that season; and it is worthy of note, that they were moving from a rock-bound coast of inaccessible cliffs, the abode of sea-birds, and exposed to the constant influence of the trade winds. No person, as far as I know, ever saw the like, except on that occasion; and I have understood that since 1811 Black Crabs have been more abundant further in to the interior of the island than they were ever known before."

Cuvier describes the Burrowing Crab as displaying wonderful instinct:—"The animal closes the entrance of its burrow, which is situated near the margin of the sea, or in marshy grounds, with its largest claw. These burrows are cylindrical, oblique, very deep, and very close to each other; but generally each burrow is the exclusive habitation of a single individual. The habit which these crabs have of holding their large claw elevated in advance of the body, as if making a sign of beckoning to some one, has obtained for them the name of Calling Crabs. There is a species observed by Mr. Bosc in South Carolina, which passes the three months of the winter in its retreat without once quitting it, and which never goes to the sea except at the epoch of egg-laying." The same observations apply to the Chevalier Crabs (so called from the celerity with which they traverse the ground). These are found in Africa, and along the borders of the Mediterranean.

Some Crabs, truly aquatic, as the Vaulted Crab of the Moluccas, have the power of drawing back their limbs, and concealing them in a furrow, which they closely fit; and thus, in imitation of a tortoise, which retracts its feet and head within its shell, they secure themselves, when alarmed. Other aquatic species have their limbs adapted for clinging to weeds and other marine objects. Of these some have the two or four hind pairs of limbs so placed as to appear to spring from the back; they terminate in a sharp hook, by means of which the Crab attaches itself to the valves of shells, fragments of coral, &c., which it draws over its body, and thus lurks in concealment. Allied, in some respects, to the Hermit or Soldier Crabs, which tenant empty shells, is one which, from its manners and habits, is one of the most extraordinary of its race. The Hermit Crabs are voracious, and feed on animal substances. The Hermit, or Bernhard Crab, is so called from its habit of taking up its solitary residence in deserted shells, thus seeking a protection for its tail, which is long and naked. It is found in shells of different dimensions, and from time to time leaves its abode, as it feels a necessity, for a more commodious dwelling. It is said to present, on such occasions, an amusing instinct as it inserts the tail successively into several empty shells until one is found to fit. We learn from Professor Bell, however, that it does not always wait until the home is vacant, but occasionally rejects the rightful occupant with some violence. On the contrary, the Crab, or rather Lobster-Crab (for it takes an intermediate place between them), is more delicate in its appetite, and feeds upon fruits, to obtain which it is said to climb up certain trees, at the feet of which it makes a burrow. This species is the Purse Crab, or Robber Crab, of Amboyna and other islands in the South Pacific Ocean.

"According to popular belief among the Indians," says Cuvier, "the Robber Crab feeds on the nuts of the cocoa-tree, and it makes its excursions during the night; its places of retreat are fissures in the rocks, or holes in the ground." The accounts of the early writers and travellers, as well as of the natives, were disbelieved; but their truth has since been abundantly confirmed. MM. Quoy and Guimard assure us that several Robber Crabs were fed by them for many months on cocoa-nuts alone; and a specimen of this Crab was submitted to the Zoological Society, with additional information from Mr. Cuming, in whose fine collection from the islands of the South Pacific several specimens were preserved. Mr. Cuming states these Crabs to be found in great numbers in Lord Hood's Island, in the Pacific. He there frequently met with them on the road. On being disturbed, the Crabs instantly assumed a defensive attitude, making a loud snapping with their powerful claws, or pincers, which continued as they retreated backwards. They climb a species of palm to gather a small kind of cocoa-nut that grows thereon. They live at the roots of trees, and not in the holes of rocks; and they form a favourite food among the natives. Such is the substance of Mr. Cuming's account. Mr. Darwin, in his "Researches in Geology and Natural History," saw several of these Crabs in the Keeling Islands, or Cocos Islands, in the Indian Ocean, about 600 miles distant from the coast of Sumatra. In these islands, of coral formation, the cocoa-nut tree is so abundant as to appear, at first glance, to compose the whole wood of the islands.

Here the great Purse Crab is abundant. Mr. Darwin describes it as a Crab which lives on the cocoa-nut, is common on all parts of the dry land, and grows to a monstrous size. This Crab has its front pair of legs terminated by very strong and heavy pincers, and the last pair by others which are narrow and weak. It would at first be thought quite impossible for a Crab to open a strong cocoa-nut, covered with the husk; but Mr. Liesk assures me that he has repeatedly seen the operation effected. The Crab begins by tearing away the husk, fibre by fibre, and always from that end under which the three eye-holes are situated. When this is completed the Crab commences hammering with its heavy claws on one of these eye-holes till an opening is made. Then, turning its body, by the aid of its posterior and narrow pair of pincers, it extracts the white albuminous substance. I think this as curious a case as I ever heard of, and likewise of adaptation in structure between two objects apparently so remote from each other in the scheme of nature as a Crab and a cocoa-nut tree. The Crab is diurnal in its habits; but it is said to pay every night a visit to the sea for the purpose of moistening its gills. These gills are very peculiar, and scarcely fill up more than a tenth of the chamber in which they are placed: it doubtless acts as a reservoir for water, to serve the Crab in its passage over the dry and heated land. The young are hatched and live for some time on the coast; at this period of existence we cannot suppose that cocoa-nuts form any part of their diet; most probably soft saccharine grasses, fruits, and certain animal matters, serve as their food until they attain a certain size and strength.

The adult Crabs, Mr. Darwin tells us, inhabit deep burrows, which they excavate beneath the roots of trees; and here they accumulate great quantities of the picked fibres of the cocoa-nut husk, on which they rest as on a bed. The Malays sometimes take advantage of the labours of the Crab by collecting the coarse fibrous substance, and using it as junk. These Crabs are very good to eat; moreover, under the tail of the larger ones there is a great mass of fat, which, when melted, yields as much as a quart bottleful of limpid oil.

The Crab's means of obtaining the cocoa-nuts have, however, been much disputed. It is stated by some authors to crawl up the trees for the purpose of stealing the nuts. This is doubted; though in the kind of palm to which Mr. Cuming refers as being ascended by this Crab, the task would be much easier. Now, Mr. Darwin states, that in the Keeling Islands the Crab lives only on the nuts which fall to the ground. It may thus appear that Mr. Cuming's and Mr. Darwin's respective accounts of the non-climbing of this Crab on the one side, and its actually climbing trees on the other, are contradictory. The height of the stem of the cocoa-nut tree, its circumference, and comparative external smoothness, would prove insurmountable, or at least very serious obstacles, to the most greedy Crab, however large and strong it might be. But these difficulties are by no means so formidable in the tree specified by Mr. Cuming: this is arborescent, or bushy, with long, thin, rigid, sword-shaped leaves, resembling those of the pineapple, usually arranged spirally, so that they are commonly called Screw Pines. They are of the genus Pandanus, a word derived from the Malay Pandang. The ascent of these arborescent plants, having the stem furnished with a rigging of cord-like roots, and bearing a multitude of firm, long, and spirally-arranged leaves, would be by no means a work of difficulty, as would necessarily be that of the tall feathery-topped cocoa-tree, destitute of all available points of aid or support. Hence the contradiction in the two accounts referred to is seeming, and not real, and the two statements are reconciled.

To sum up, Mr. Cuming fully testifies to the Crab climbing the Screw Pines; and he has told Professor Owen that he has actually seen the Crab climbing the cocoa-nut tree. The Crab has been kept on cocoa-nuts for months; and is universally reported by the natives to climb the trees at night.

We may here, too, observe, that fine specimens of the Climbing Crab are to be seen in the British Museum. Here, too, arranged in cases, are Spider Crabs; Crabs with oysters growing on their backs, thus showing that Crabs do not shed their shells every year, or that the oyster increases very rapidly in bulk; Oval-bodied Crabs; and Fin-footed or Swimming Crabs. Here are also Telescope, or Long-eyed Crabs, and Land Crabs, found in India 4,000 feet above the sea-level; another of similar habits in the plains of the Deccan, that may be seen swarming in the fields, some cutting and nipping the green rice-stalks, and others waddling off backwards with sheaves bigger than themselves. To these may be added Square-bodied Crabs, Crested Crabs; Porcelain Crabs, with delicate, china-like shells; and Death's-head Crabs, which usually form cases for themselves from pieces of sponge and shells.

Certain species of Crabs are remarkably tenacious of life, and have been known to live for weeks buried, and without food. It is in the Crab tribe that the fact of the metamorphosis of crustacea has been most distinctly perceived; a small, peculiar crustacean animal, that had long passed for a distinct species, under the name of Zoea, having at length been identified with the young of the common Crab before it had attained its full development.

That among the Crab tribes a tree-climbing species is to be found is certainly curious, but it is not without a parallel among fishes. Many of the latter leave the water, some even for a long time, and perform overland journeys, aided in their progress by the structure of their fins. In these fishes the gills and gill-chambers are constructed for the retention of water for a considerable time, so as to suffice for the necessary degree of respiration. In our country, we may mention the eel, which often voluntarily quits the river or lake, and wanders during the night over the adjacent meadows, probably in quest of dew-worms. But the marshes of India and China present us with fishes much more decidedly terrestrial, and some of which were known to the ancients. Among these are several fishes of a snake-like form: they have an elongated, cylindrical body, and creep on land to great distances from their native waters. The boatmen of India often keep these fishes for a long time out of water, for the sake of diverting themselves and others by their terrestrial movements, and children may often be seen enjoying this sport.

Of these land-haunting fishes, the most remarkable is the tree-climber, so called in Tranquebar. This fish inhabits India, the Indian islands, and various parts of China, as Chusan, &c., living in marshes, and feeding on aquatic insects, worms, &c. According to Daldorf, a Danish gentleman, who, in 1797, communicated an account of the habits of this fish to the LinnÆan Society, it mounts up the bushes or low palms to some elevation. This gentleman states that he had himself observed it in the act of ascending palm-trees near the marshes, and had taken it at a height of no less than five feet, measured from the level of the adjacent water. It effects its ascent by means of its pectoral and under fins, aided by the action of the tail and the spines which border the gill covers. It is by the same agency that it traverses the land. The statement of M. Daldorf is corroborated by M. John, also a Danish observer, to whom we are indebted for the knowledge of its name in Tranquebar, which alludes to its arboreal proceedings.

It is true that many other naturalists who have observed the habits of this fish in its native regions, while they concur in describing its terrestrial journeys, and its living for a long time out of water, either omit to mention, or mention with doubt, its reputed attempts at tree-climbing.

The habits and instincts of certain Crawfishes are very extraordinary. Thus, the Astaci are migratory, and in their travels are capable of doing much damage to dams and embankments. On the Little Genesee River they have, within a few years, compelled the owner of a dam to rebuild it. The former dam was built after the manner of dykes, i.e., with upright posts, supporting sleepers, laid inclining up the stream. On these were laid planks, and the planks were covered with dirt. The Astacus proceeding up the stream would burrow under the planks where they rested on the bottom of the stream, removing bushels of dirt and gravel in the course of a night. They travel over the dam in their migrations, often climbing posts two or three feet high to gain the pond above. [22]

We have to add a new and eccentric variety of nature—the Pill-making Crab, which abounds at Labuan, Singapore, and Lahore, and is described in Mr. Collingwood's "Rambles of a Naturalist." When the tide is down, this little creature, if stealthily watched, may be seen creeping up a hole in the sandy shore, taking up rapidly particles of the loose powdery sand in its claws, and depositing them in a groove beneath the thorax. A little ball of sand, about the size of a filbert, is forthwith projected, though whether it passes actually through the mouth is not made clear. Pill after pill is seized with one claw, and laid aside, until the beach is covered with these queer little pellets. This is evidently the creature's mode of extracting particles of food from the sand.

Mr. Collingwood also describes, as met with on the shores and waters of the China seas, Glass Crabs, whose flat, transparent, leaf-like bodies seem made of fine plates of mica. The dredge brings up many a rich haul of sponges, corals, and gorgoniÆ, of the most splendid colours, certain of the sponges harbouring within their cells minute crabs of a new genus. Between Aden and Galle the sea is of a pinkish colour, owing to the immense accumulation of minute kinds of medusÆ, in solid masses of red jelly. Over Fiery Cross Reef, the mirror-like sea reveals, at the depth of sixty or seventy feet, this wealth of natural treasures. "Glorious masses of living coral strew the bottom: immense globular madrepores—vast overhanging mushroom-shaped expansions, complicated ramifications of interweaving branches, mingled with smaller and more delicate species—round, finger-shaped, horn-like and umbrella-form—lie in wondrous confusion. Here and there is a large clam-shell, wedged in between masses of coral, the gaping, zigzag mouth covered with the projecting mantle of the deepest Prussian blue; beds of dark purple, long-spined Echini, and the thick black bodies of sea-cucumbers vary the aspect of the sea bottom." [23]

FOOTNOTES:

[21] This Crab has an elongated spine-like tail, the use of which was long misunderstood. Dr. J. Gray was shown at the Liverpool Museum some living King Crabs, and the use they made of the tail-like appendages. When turned over on their backs, he saw them bend down the tail until they could reach some point of resistance, and then employ it to elevate the body, and regain their normal position. Dr. Gray states that they never have been seen to use this tail for the purpose which has been often assigned to it—that is, for leaping from place to place by bending it under the body, like the toy called a "spring-jack," or "leaping frog." [22] American Journal of Science and Art. [23] W. C. LinnÆus Martin, F.L.S.