Part 19

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.

MUSICAL LIZARDS.

A small Lizard, lately brought home from the Isle of Formosa by Mr. Swinhoe, is decided to be a new species by Dr. Günther, of the British Museum. Mr. Swinhoe found the eggs of this Gecko, or Lizard, in holes of walls or among mortar rubbish. They are round, and usually lie several together, resembling eggs of ordinary Lizards. The young, when first hatched, keep much under stones in dark cellars, where they remain until they attain about two-thirds of the adult size, when they begin to appear in public to catch insects, but evincing great shyness of their seniors. Mr. Swinhoe states that on the plaster-washed sides of his bedroom, close to the angle of the roof, every evening when the lamp was placed on the table below, four little Musical Lizards used to make their appearance and watch patiently for insects attracted by the light. A sphinx or a beetle buzzing into the room would put them into great excitement, and they would run with celerity from one part of the wall to the other after the deluded insect as it fluttered in vain, buffeting its head, up and down the wall. Two or three would run after the same insect, but as soon as one had succeeded in securing it, the rest would prudently draw aloof. In running over the perpendicular face of the wall they keep so close, and their movements are made so quickly, with one leg in advance of the other, that they have the appearance at a distance of gliding rather than running. The tail is somewhat writhed as the body is jerked along, and much so when the animal is alarmed and doing its utmost to escape; but its progress even then is in short runs, stopping at intervals and raising its head to look about. If a fly perch on the wall it cautiously approaches to within a short distance, then suddenly darts forwards, and with its quickly-protruded, glutinous tongue, fixes it. Apart from watching its curious manoeuvres after its insect-food, the attention of the most listless would be attracted by the singular series of loud notes these creatures utter at all hours of the day and night, more especially during cloudy and rainy weather. These notes resemble the syllables "chuck-chuck," several times repeated; and, from their more frequent occurrence during July and August, they are thought to be the call notes of the male to the female.

During the greater part of the day, the little creature lies quiescent in some cranny among the beams of the roof or in the wall of the house, where, however, it is ever watchful for the incautious fly that approaches its den, upon whom it darts forth with but little notice. But it is by no means confined to the habitations of men. Every old wall, and almost every tree, possesses a tenant or two of this species. It is excessively lively, and even when found quietly ensconced in a hole, generally manages to escape--its glittering little eyes (black, with yellow ochre iris) appearing to know no sleep; and an attempt to capture the runaway seldom results in more than the seizure of an animated tail, wrenched off with a jerk by the little fellow as it slips away, without loss of blood. The younger individuals are much darker than the larger and older animals, which are sometimes almost albinoes. In ordinary fly-catching habits, as they stick to the sides of a lamp, there is much similarity between this gecko and the little papehoo, or wall-lizard of China; but this is decidedly a larger and much more active animal, and often engages in a struggle with insects of very large size. The Chinese colonists of Formosa greatly respect the geckos, in consequence of a legend which attributes to them the honour of having once poisoned the supplies of an invading rebellious army, which was thereby totally cut to pieces. The geckos were raised to the rank of generals by the grateful Emperor of China; which honour, the legend states, they greatly appreciated, and henceforth devoted their energies to the extermination of mosquitoes and other injurious insects.

CHAMELEONS, AND THEIR CHANGES.

"Nil fuit unquam Sic impar sibi."--_Horat._

"Sure such a various creature ne'er was seen."

_Francis, in imit._

The Chameleon tribe is a well-defined family of lizard-like reptiles, whose characters may be summed up as existing in the form of their feet; the toes, which are joined together or bound up together in two packets or bundles, opposed to each other; in their shagreen-like skin; in their prehensile tail; and in their extensile and retractile vermiform tongue.

That the Chameleon was known to the ancients there is no doubt. Its name we derive directly from the _Chamelæo_ of the Latins. Aristotle's history of the animal proves the acute observation of that great zoologist--the absence of a sternum, the disposition of the ribs, the mechanism of the tail, the motion of the eyes, the toes bound up in opposable bundles, &c.--though he is not entirely correct on some points. Pliny mentions it, but his account is for the most part a compilation from Aristotle.

Calmet's description of the Chameleon is curiously minute:--"It has four feet, and on each foot three claws. Its tail is long: with this, as well as with his feet, it fastens itself to the branches of trees. Its tail is flat, its nose long, ending in an obtuse point; its back is sharp, its skin plaited, and jagged like a saw, from the neck to the last joint of the tail, and upon its head it has something like a comb; like a fish, it has no neck. Some have asserted that it lives only upon air, but it has been observed to feed on flies, catched with its tongue, which is about ten inches long and three thick, made of white flesh, round, but flat at the end, or hollow and open, resembling an elephant's trunk. It also shrinks, and grows longer. This animal is said to assume the colour of those things to which it is applied; but our modern observers assure us that its natural colour, when at rest, and in the shade, is a bluish-grey; though some are yellow, others green, but both of a smaller kind. When it is exposed to the sun, the grey changes into a darker grey, inclining to a dun colour, and its parts which have least of the light upon them are changed into spots of different colours. Sometimes, when it is handled, it seems speckled with dark spots, inclining to green. If it be put upon a black hat, it appears to be of a violet colour; and sometimes, if it be wrapped up in linen, it is white; but it changes colour only in some parts of the body."

Its changes of colour have been commemorated by the poets. Shakspeare has--

"I can add colours ev'n to the Chameleon: Change shapes with Proteus, for advantage."

Dryden has--

"The thin Chameleon, fed with air, receives The colour of the thing to which it cleaves."

Prior has--

"As the Chameleon, which is known To have no colours of his own, But borrows from his neighbour's hue His white or black, his green or blue."

Gay, in his charming fable of the Spaniel and the Chameleon, "scarce distinguished from the green," makes the latter thus reply to the taunts of the pampered spaniel:--

"'Sir,' says the sycophant, 'like you, Of old, politer life I knew: Like you, a courtier born and bred, Kings lean'd their ear to what I said: My whisper always met success; The ladies prais'd me for address; I knew to hit each courtier's passion, And flatter'd every vice in fashion: But Jove, who hates the liar's ways, At once cut short my prosperous days, And, sentenced to retain my nature, Transform'd me to this crawling creature. Doom'd to a life obscure and mean, I wander'd in the silvan scene: For Jove the heart alone regards; He punishes what man rewards. How different is thy case and mine! With men at least you sup and dine; While I, condemned to thinnest fare, Like those I flatter'd, fed on air.'"

Upon this fable a commentator acutely notes:--"The raillery at court sycophants naturally pervades our poet's writings, who had suffered so much from them. Here, however, he intimates something more, namely, the apposite dispensations to man's acts, even in this world. The crafty is taken in by his own guile, the courtier falls by his own arts, and the ladder of ambition only prepares for the aspirant a further fall."[24]

With respect to the air-food of the Chameleon. Cuvier observes that its lung is so large that, when it is filled with air, it imparts a transparency to the body, which made the ancients say that it lived upon air; and he inclines to think that to its size the Chameleon owes the property of changing its colour; but, with regard to this last speculation, he was wrong, as we shall presently see.