In the last four genera it will be perceived that the maxillipeds do not form a complete operculum, but by the arrangement of the inner edges of their third and fourth. joints they leave a lozenge-shaped space over the mouthopening uncovered, while in Uca and Gecarcinucus the straight inner edges from either side can be brought exactly together so as to close the cavity completely. Mr. WoodMason points out that the character of the exopod distinguishes Gecarcinus, Gecarcoidea (which he calls Pelocarcinus), and Hylaeocarcinus from the three preceding genera, and that they are distinguished from one another by a further character of the maxillipeds, for in Gecarcinus the three terminal joints are completely hidden, in Hylæocarcinus they are partially visible, and in Gecarcoidea completely so.

None of the Crustacea have more attracted the attention and excited the wonder of travellers than some of those belonging to this group. Like the twin snakes that came over the sea and deliberately landed at Troy to slay Laocoon and his two sons, these crabs have, contrary to nature, forsaken the ample waters of the ocean, scorned all the brooks and rivers and lakes, and carried out a portentous invasion of the dry land. Still they are by no means indifferent to moisture. The vaulted part of the carapace over the branchial regions is lined with a very spongy membrane, and sometimes a fold of the membrane along the lower edge of the cavity forms a kind of tube in which water may be held as in a reservoir. But their form and structure are not so surprising as their manners and customs.

Under the heading Cancer ruricola, a species of Gecarcinus, Herbst brings together many curious particulars, depending largely upon Patrick Browne's History of Jamaica.' In the Bahamas, he says, and in tropical regions these land-crabs are so numerous that when they creep out of their holes the ground seems to be in motion. One little island is so full of them that it has been called Crab Island. They are just as frequent in certain districts of Jamaica and in some of the Caribbee islands. The same

REMARKABLE BEHAVIOUR

81

was the case at St. Croix, but since the cutting down of the forests and destruction of thousands of the crabs, their number has diminished. They generally take up their abode on the hills, not less than one mile nor more than three miles from the coast. It is in the morning and evening that they are to be found in greatest numbers under the trees. Go away then without a stick in hand, and they will approach with uplifted claws as if threatening an assault. But if they are themselves assailed with a stick or a switch, they retreat, yet still facing the foe, and ever and anon clashing their claws together to strike terror into him. Thus they withdraw to their holes in the rock or the rotten tree or deep burrows in the ground. They are capital eating, and are one of the principal food resources of the natives, who improve the flavour by fattening them up for three or four days in a potato field. But a warning is given that they do not always suit the stomach of Europeans, since they are apt to produce cold hypochondriac humours, whereby some explain the slow melancholy nature of the Caribbee islanders. When seized by a leg or a claw these crabs relinquish it so readily as to produce the impression that their limbs are only stuck on. The lost appendage would be renewed at the next change of skin, but it often happens that the sacrifice which has saved the crab from its human foes exposes it as a defenceless victim to those of its own race.

The pairing season is said to be in March and April. In May, the rainy period, they march in great hosts towards the sea, to bathe and lay their eggs in it. 'Then all roads

and brooks are filled with them, and it is indeed a very wonderful instinct, which the Creator has given them, to go direct to that part of the island where there are stretches of sand and slopes from which they can most easily arrive at the sea. Nothing can hinder them from going the straight road towards the sea, for they go over everything that comes in their way, be it hedges, houses, churches, hills or cliffs, straight over everything they go, and rather clamber up at the peril of their lives, than make a circuit. In the night, for example, they will creep in at a window, and

G

come on to the beds, causing the unwary occupants no small alarm by their clatter. If one has the misfortune to tumble down and damage its limbs, it is immediately eaten up by the rest. It must be a wonderful sight, to see them come down the hills. Everywhere they issue from hollow trees, rotten stems, from under the rocks, and out of innumerable holes. The fields are so covered with them, that unless they are chivied away, there is no setting foot to ground without treading upon them. What with the infinite variety of their markings, their brilliant colours, their sideways gait, their celerity, I know, of scarcely any sight comparable with this one. Unless the description of their march has been embellished by the force of imagination, the journey is conducted with as much order as if they had a very experienced commander.' The vanguard, consisting of none but males, starts some days in advance. Then follows the main army, composed chiefly of females, their battalions often covering a space of a mile and a half long by forty or fifty paces broad, and covering it so closely as almost to hide the ground. Some days after, the rear-guard, containing both males and females, closes the vast procession.

Sometimes all the divisions are brought to a halt several days by the want of rain, a want which makes prolonged land-travel impossible to a crustacean. But when Herbst says that these hosts follow the line of the rivers and watercourses, the statement, though highly probable in itself, is scarcely consistent with the miraculous bee-line which he had previously described. If anyone approaches the army and puts it into alarm, these martial crabs draw back facing him, with their claws uplifted and open to be constantly ready for defence. The nip of one of them, it is said, can tear out a piece of flesh, and the claw, even after it has been thrown off by its owner, will continue for a minute to pinch with incredible force. The noise of their march is compared to the rattling of the armour of a regiment of Cuirassiers. Having arrived on the coast, they bathe once in the sea, and then creep into some shelter to rest. The females enter the sea a second time and there deposit their

SEASIDE LODGINGS

83

eggs. These are cast up by the waves upon the sand, and in due course out creep the young crabs, which then cling to the rocks in thousands, but presently quit the water for any suitable places of protection on land, there acquiring strength to follow their mothers up the country.

Patrick Browne says: "The eggs are discharged from the body through two small round holes situated at the sides, and about the middle of the under shell; these are only large enough to admit one at a time, and, as they pass, they are entangled in the branched capillaments, with which the outer side of the apron is copiously supplied, to which they stick by means of their proper gluten, until the creatures reach the surf, where they wash 'em all off, and then they begin to return back again to the mountains. It is remarkable that the bag or stomach of this creature changes its juices with the state of the body; and, while poor, is full of a black, bitter, disagreeable fluid, which diminishes as it fattens, and, at length, acquires a delicate rich flavour. About the month of July or August the crabs fatten again, and prepare for mouldering, filling up their burrow with dry grass, leaves, and abundance of other materials; when the proper period comes, each retires to his hole, shuts up the passage, and remains quite inactive, until he gets rid of his old shell, and is fully provided with a new one. How long they continue in this state is uncertain, but the shell is first observed to burst both at the back and sides, to give a passage to the body, and it extracts its limbs from all the other parts gradually afterward. At this time the fish is in the richest state, and covered only by a tender membranous skin variegated with a multitude of reddish veins, but this hardens gradually after, and becomes soon a perfect shell like the former; it is, however, remarkable that during this change there are some stony concretions always found in the bag, which waste and dissolve gradually, as the creature forms and perfects its new crust. A wonderful mechanism!' A footnote remarks that the concretions, which are the wellknown gastroliths or crab's eyes, are seldom under two or more than four.'

Since it is during this period of mouldering' that the crabs are fattest and best flavoured, Herbst finds it easy to suppose that greedy man will not leave them safe in their repose. On the contrary, he busily digs them out with a spade. Considering how readily under some circumstances these crustaceans shed their limbs, it is singular that in exuviation they are able to cast off their whole caparison so uninjured and complete that it might be mistaken for the living animal. Careful inspection is required to perceive near the insertions of the limbs the ventral slit through which the animal has made its escape.

It was in a West Indian species of Gecarcinus that Professor Westwood observed that the young issued from the egg in a form not materially different from that of their parents. This experience, combined with Rathke's similar observation in regard to the European crayfish, led him at first to throw doubt upon Vaughan Thompson's theory of crustacean metamorphoses. But it was soon brought to light that the examples of the land-crab and the freshwater crayfish were interesting exceptions to a still more interesting rule, and there are few who would now deny that these exceptions are to be explained as modifications in the life-history of the animals concerned, acquired late in the course of time to suit the new conditions of existence encountered by creatures emerging from the sea to a life in fresh water or on dry ground. That no crustaceans have been able to cut themselves loose from some dependence upon moisture is not very wonderful, since in that respect man himself is still an aquatic animal.

Gecarcinus lagostoma, Milne-Edwards, represented on Plate II, is a widely distributed species.

Hylaeocarcinus Humei, Wood-Mason, occurs in the dark dense damp forests of the Nicobar Islands.'

Uca una (Linn.), the crab of the mangrove swamps of Brazil, may be mentioned as a rare instance of one that has been allowed to possess the names by which it was figured and described centuries ago. In this genus the last joints of the walking legs are compressed and un