The

crab from its residence, and laying it flat before him. Robber Crab, however, does not live in a shell, and its abdomen is consequently defended by hard plates, instead of being soft and unprotected like that of the hermit crab, to which it is closely allied.

The Robber Crab inhabits the islands of the Indian ocean, and is one of those crustacea which are able to exist for a long time without visiting the water, the gills being kept moist by means of a reservoir on each side of the cephalothorax, in which the organs of respiration lie. Only once in twenty-four hours does this remarkable crab visit the ocean, and in all probability enters the water for the purpose of receiving the supply which preserves the gills in working order.

It is a quick walker, though not gifted with such marvellous speed as that which is the property of the racer and other land crabs, and is rather awkward in its gait, impeded probably by the enormous claws. While walking, it presents a curious aspect, being lifted nearly a foot above the ground on its two central pairs of legs, and if it be intercepted in its retreat, it brandishes its formidable weapons, clattering them loudly, and always keeping its face towards the enemy. Some writers aver that it is capable of climbing up the stems of the palm-trees, in order to get at the fruit, but this assertion seems to require very strong corroboration before it can be believed.

The food of the Robber Crab is of a very peculiar nature, consisting chiefly, if not entirely, of the cocoa-nut. Most of my readers have seen this enormous fruit as it appears when taken from the tree, surrounded with a thick massy envelope of fibrous substance, which, when stripped from the nut itself, is employed for many useful purposes. How the creature is to feed on the kernel seems quite a mystery; and, primâ facie, for a crab to extract the cocoa-nut from its envelope, to pierce the thick and stubborn shell, and to feed upon the enclosed kernel, seems an utterly impossible task. Indeed, had not the feat been watched by credible witnesses, no one who was acquainted with the habits and powers of the crustacea would have credited such an assertion. Yet Mr. Darwin, Messrs. Tyerman and Bennett, and other observant men, have watched the habits of the creature, and all agree in their accounts.

According to Mr. Darwin, the crab seizes upon the fallen

cocoa-nuts, and with its enormous pincers tears away the outer covering, reducing it to a mass of ravelled threads. This substance is carried by the crabs into their holes, for the purpose of forming a bed whereon they can rest when they change their shells, and the Malays are in the habit of robbing the burrows of these stored fibres, which are ready picked for them, and which they use as "junk," i.e. a rough kind of oakum, which is employed for caulking the seams of vessels, making mats, and similar purposes. When the crab has freed the nut from the husk, it introduces the small end of a claw into one of the little holes which are found at one end of the cocoa-nut, and by turning the claw backwards and forwards, as if it were a bradawl, the crab contrives to scoop out the soft substance of the nut.

According to the observations of Messrs. Tyerman and Bennett, the well-known missionaries to the South Seas, the Robber Crab has another method of getting at the cocoa-nut, and displays an instinctive knowledge of political economy which is very remarkable.

These animals live under the cocoa-nut trees, and subsist upon the fruit which they find upon the ground. With their powerful front claws they tear off the fibrous husk; afterwards, inserting one of the sharp points of the same into a hole at the end of the nut, they beat it with violence against a stone until it cracks; the shell is then easily pulled to pieces, and the precious fruit within devoured at leisure. Sometimes, by widening the hole with one of their round, gimlet claws, or enlarging the breach with their forceps, they effect sufficient entrance to enable them to scoop out the kernel, without the trouble of breaking the unwieldy nut.

"These crabs burrow in the earth, under the roots of the trees that furnish them with provisions-prudently storing up in their holes large quantities of cocoa-nuts, stripped of their husk, at those times when the fruits are most abundant, against the recurring intervals when they are scarce. We are informed that if the long and delicate antennæ of these robust creatures be touched with oil, they instantly die. They are not found on any of these islands except the small coral ones, of which they are the principal occupants. The people here account them delicious

food."

The palm-climbing habits of the Robber Crab are mentioned

by Mr. T. H. Hood, in his "Notes of a Cruise in H.M.S. Fawn, in the Western Pacific." In the Samoan group of islands, the crab is called "Ou-ou,” and is a favourite article of food. While the vessel remained off Samoa, Mr. Hood asked about these crabs; and though he did not see any of them performing so strange a feat, he shows that there are very good grounds for believing the possibility of such an action.

"I inquired of them about the habits of the Ou-ou, or great cocoa-nut-eating crab, common here, and found the reports previously received from the natives corroborated. Mr. Darwin mentions that, in the Seychelles and elsewhere, there is a species which is in the habit of husking the nuts on the ground, and then tapping one of the eyes with its great claw, in order to reach the kernel. Its congener here ascends the cocoa-trees, and having thrown the nuts down, husks them on the ground; this operation performed, again ascends with the nuts, which he throws down, generally breaking them at the first attempt, but, if not successful, repeating it till the object is attained.

"Before leaving, an old Savage Island man at the mission brought in three or four immense Ou-ous, which evinced in their efforts to escape, bursting coils of cocoa-nut sinnet, a strength quite sufficient to husk the toughest cocoa-nut. As to the method of obtaining the contents afterwards, every native (both Samoans and Niuans) confirms the account mentioned before. The Niuans understand their habits best. The old man who brought them to-day dug them out of the holes in which they remain many weeks torpid. The female differs from the male in having three flippers, well furnished with strong borers, on the right side of the sac."

When full grown, this crab is more than two feet in length, and, as may be seen by the illustration, is stoutly made in proportion to its length. The colour of the creature is very pale brown, with a decided tinge of yellow.

PASSING by many other species of crustacea which burrow in the earth, or mud, or sand, we come to a very remarkable being, which makes its habitation in solid wood. This is the WOODBORING SHRIMP (Chelura terebrans), one of the sessile-eyed crustacea, nearly related to the well-known sand-hopper, which is so plentiful on our coasts.

Although very small, it is terribly destructive, and does no small damage to wooden piles driven into the bed of the sea. It is furnished with a peculiar rasping instrument, by means of which it is enabled to scrape away the wood and form a little burrow, in which it resides, and which supplies it with nourishment as well as with a residence. The tunnels which it makes are mostly driven in an oblique direction; so that when a large number of these creatures have been at work upon a piece of timber, the effect of their united labours is to loosen a flake of variable dimensions. As long as the weather is calm, the loosened flake keeps its position; but no sooner does a tempest arise, than the flake is washed away, and a new surface is exposed to the action of the Chelura.

When the Chelura is placed on dry land, it is able to leap nearly as well as the sand-hopper, and performs the feat in a similar manner.

THIS is not the only wood-boring crustacean with which our coasts are pestered; for the GRIBBLE (Limnoria terebrans) makes deeper tunnels than the preceding creature, though it is not so rapidly destructive, owing to the direction of its burrows, which are driven straight into the wood, and do not cause it to flake off so quickly as is the case when the Chelura excavates it. Still, it works very great harm to the submerged timber, boring to a depth of two inches, and nearly always tunnelling in a straight line, unless forced to deviate by a nail, a knot, or similar obstacle. The Gribble is a very tiny creature, hardly larger than a grain of rice, and yet, by dint of swarming numbers, it is able to consume the wooden piles on which certain piers and jetties are supported; and in the short space of three years these destructive crustacea have been known to eat away a thick fir plank, and to reduce it to a mere honeycomb. Sometimes these two wood-boring shrimps attack the same piece of wood, and, in such cases, the mischief which they perpetrate is almost incredible, considering their small dimensions and the nature of the substance into which they bore. The common fresh-water shrimp, so plentiful in our brooks and rivulets, is closely allied to the Gribble, and will convey a very good idea of its appearance. In some parts of our coasts the ravages of these animals are so destructive, that the substitution of iron or stone for wood has become a necessity.

CHAPTER V.

BURROWING MOLLUSCS.

The BORING SNAIL of the Bois des Roches-Opinions as to its method of burrowing-Shape of the tunnels-Solitary habits of the Snail-The PIDDOCK, its habits and appearance-Structure of the Shell, and its probable useMethod of barrowing-Use of the Piddock and other marine burrowers-The balance of Nature preserved─The WOOD-BORER and its habits-The DATE SHELL-Its extraordinary powers of tunnelling-The RAZOR SHELL-Its localities and mode of life-The FLASK SHELL and the WATERING-POT SHELL-The SHIPWORM-Its appearance when young and adult-Its curious developmentIts ravages, and the best method of checking them-Its value to engineersThe GIANT TEREDO-Form, dimensions, and structure of the shell-How and where discovered.

ILL fitted as the Molluscs seem to be for the task of burrowing, there are several species which are able not only to make their way through soft mud, or into the sandy bed of the sea, but to bore deep permanent tunnels into stone and wood. Even the hard limestone and sound heart-of-oak timber cannot defy these indefatigable labourers, and, as the sailor or the dweller on the coast knows full well, the rocks and the timber are often found reduced to a mere honey-combed or spongy texture by the innumerable burrows of these molluscs.

THERE is now before me a piece of very hard calcareous rock, in which are bored several deep holes, large enough to admit a man's thumb, and remarkably smooth in the interior, the extremity being always rounded. Indeed, if a hole were made in a large lump of putty by putting the thumb into it and turning it until the sides of the hole became smooth, a very good imitation of these miniature tunnels would be produced. This fragment of stone was taken from a little wood in Picardy, called Le Bois des Roches, on account of the rocky masses that protrude through its soil, and was brought to England by Mr. H. J. B. Hancock, who kindly presented it to me.