CHAPTER XVII.

THE CRUSTACEA.

"Multa tamen lætus tristia pontus habet."

OVID.

The animals of this class, as regards organisation, must be placed higher in the scale than the Arachnidæ, or spiders; but they are beneath the Mollusca, although as regards affinity, the Mollusca in their lower division--the Molluscoïda--more approximate to the Polyp class than to the Crustacea.

The Crustacea is the highest division of articulate animals with feet; they breathe by means of gills, and have no stigmata, or air-passages, as in insects. The name signifies a hard crust or covering, with which the animals are protected. This consists of layers of carbonate of lime with one of pigment, generally, but not always, on the surface. The general outline of these animals is peculiar; unlike insects, they are not divisible into head, thorax, and abdomen; many species truly have no head at all; but a pair of eyes point to the seat of intelligence. Most of these animals have two compound eyes; but a few, like some insects, have both simple and compound eyes. The mouth is situated in the under part of the anterior of the body: in some cases they have jaws, as in crabs; in others suckers only.

Passing over the vast numbers of beings which inhabit the debatable ground--the _Annelids_, which were for ages confounded with the worms, because of their resemblance in form:--a form which might be declared forbidding, but, as Aristotle has well said, Nature, in her domain, knows nothing low, nothing contemptible; the sea-leeches, whose condition was an impenetrable mystery to Pliny, "Omnia incerta ratione, et in naturæ majestate abdita;" and the singular cirripedes, one species of which, the barnacle (_Anatifa lævis_), was thought by old Gerard, the herbalist, and in his day by many others, to be the egg from which the barnacle goose was produced--passing over these ocean tribes, we reach the Crustaceans--the Insects of the Sea; of greater size, force, and voracity than any land insect with which we are acquainted. They are armed, also, at all points; for, in place of the coriaceous tunic, they are clothed in calcareous armour, both hard and strong, and bristling with coarse hairs, spiny tubercles, and even serrated spines.

The Crustaceans have nearly all of them claws, formidably hooked and toothed, which they employ as pincers, both in offensive and defensive war. They have been compared to the heavily-armed knights of the middle ages--at once audacious and cruel; barbed in steel from head to foot, with visor and corslet, arm-pieces and thigh-pieces--nothing, in fact, is wanting to complete the resemblance.

These marine marauders live on the sea-coast, among the rocks, and near the shore. Some few of them frequent the deep waters, others hide themselves in the sand or under stones, while the common crab (_Carcinus mœnas_, Leach) loves the shore almost as much as the salt water, and establishes itself accordingly under some moist cliff overhanging the sea, where it can enjoy both.

One of the necessary consequences of the condition of these animals, enclosed in a hard shell, is their power of throwing it off. The solidity of their calcareous carapace would effectually prevent their growth, but at certain determinate periods Nature despoils the warrior of his cuirass; the creature moults, and the calcareous crust falls off, and leaves it with a thin, pale, and delicate tunic. In this state the Crustacean is no longer worthy of its name--its skin has become as vulnerable as that of the softest mollusc; but it has the instinct of weakness--it retires into lonely places, and hides its shame in some obscure crevice, until another vestment, more suitable for resistance, and adapted to its increased size, has been restored.

The Crustacean has not a vertebral column. The covering of the Crustacean consists of a great number of distinct pieces, connected together by means of portions of the epidermis which have not yet become hardened, in the same way as the bones in the skeleton of the vertebrata are connected by cartilages, the ossification of which only takes place in old age. The covering of the Crustacean consists of a series of rings varying in number, the normal number of the body-segments being twenty-one. Each ring is divisible into two arcs--one upper, or dorsal, the other lower, or ventral; and each arc may present four elementary pieces, two of which are united in the mesial line from the _tergum_, or back; the lower arc is a counterpart of this, while the others form the two side, or epimeral, pieces. The skin, therefore, performs the functions of a skeleton, so that the Crustaceans, as was said by Geoffroy Saint Hilaire, like the molluscs, live inside and not outside the bony column. The analogue of the Crustacea amongst vertebrata is to be found amongst Sturgeonidæ, whose hard, immovable bony case encloses a softer skeleton; agreeing in its characters with that of the higher divisions of vertebrata, although not possessing the solidity of bone.

The Crustaceans vary greatly in colour; some are of a dark, iron-grey, with a dash of steel-blue, like metal weapons forged for combat; a few of them are red, or reddish-brown; others are of an earthy yellow, or of a livid blue.

"The integument," according to Milne Edwards, "consists of a _corium_, or true skin, and epidermis, with a pigmentary matter, which colours the latter. The corium is a thick, spongy, and vascular membrane, connected with the serous substance which lines the parietal walls of the cavities, as the serous membrane lines the internal cavities among the vertebrata." This pigment is less a membrane than an amorphous matter diffused through the outer layer of the superficial membrane, which changes to red in the greater number of species in alcohol, ether, acids, and water at 212° Fahr.

The calcareous crust of the animal is thick, and in the dorsal region capable of great resistance; their members are also of remarkable hardness; but in the smaller species the shell is often thin, and of that crystalline transparency which permits of its digestion and circulation being observed. Many species, which are quite microscopic, contribute colour to the sea--red, purple, or scarlet: such are _Grimothea D'Urvillei_ and _G. gregarea_.

Before the year 1823, it was not generally supposed that this class of animals was subject to change of shape from the larva condition, and during its progressive development; but about this time, and for some years following, certain able microscopic experiments clearly demonstrated that a minute nondescript kind of animal called the _Zoea Taurus_, was nothing more nor less than the young of a kind of Prawn as when extracted from the egg. Mr. Vaughan Thomson, by many successive observations, and under the fire of much adverse criticism, satisfactorily established the truth of metamorphic change in many genera, and, in particular, in regard to the common crab (_Cancer pagurus_); having succeeded in hatching the ova of this species, the product of which were fine Zoeas. That there are variations in the channel of this law of change has been admitted, but that generally a metamorphosis exists, analogous to that of insects, in the various genera of Crustacea, with hardly an exception, has been clearly established.

The recorded observations of the eminent naturalist we have mentioned, Mr. Thomson, as well as those of Mr. Couch, of Penzance, Mr. Milne Edwards, and particularly those of the last mentioned, the learned author of perhaps the best work extant on the Crustacea, are referred to as treating most lucidly on this interesting subject.

As an illustration of this metamorphosis, we give figures of the _Zoea Taurus_ in two states, viz., Fig. _a_, in the first stage; and second, Fig. _b_, as the animal appeared on the fourth day after the first microscopic examination, and when it resolved itself into a kind of prawn. The drawings appear in Mr. Bell's "History of British Stalk-eyed Crustacea," and were taken by that gentleman from the work of a Dutch naturalist, named Slabber, who made the original observation in the year 1768, and published the result in 1778, from which time the subject had been allowed to fall asleep until revived by Mr. Thomson.

Among the sea-spiders, which have no neck (_Cephalothorax_), the head gradually disappears in the breast, but the belly remains distinct; the middle of the body is compressed, the shape narrow and graceful. Among the Crustaceans which have neither neck nor shape, the head, the breast, and the belly form only one mass, often short, squat, athletic, and difficult to take, as in _Pisa tetraodon_ (Fig. 332), the four-horned spider-crab.

Many of these animals have a powerful tail, consisting of a certain number of ciliated paddles, which it uses in swimming to beat the water, and to confuse its enemies.

The Crustaceans, so far as they are aquatic, respire by means of _branchiæ_, or gills. In the larger species these branchiæ are lamellous, or with filaments, whose supports are traversed by two canals, one of which leads the blood into the general economy, the other directs it towards the heart. These organs are enclosed in the body. In the smaller species the branchiæ often appear exteriorly, hanging in the water like a fungus. Sometimes these are at once swimming and breathing organs; in other cases the animal has no special organs of respiration.

Nearly all the Crustaceans are strong, hardy, and destructive, forming a horde of nocturnal brigands--merciless marauders, who recoil from no trap in which they can lie in wait for their prey. They fight _à l'outrance_ not only with their enemies, but often among themselves, either for a prey or for a female, sometimes for the sake of the fight. The miserable creatures struggle audaciously with their claws. The carapace generally resists the most formidable blows; but the feet, the tail, and, above all, the antennæ, suffer frightful mutilation. Happily for the vanquished, the mutilated members sprout again after a few weeks of repose. This is the reason for the many Crustaceans met with having the talons of very unequal size: the smaller are those lost in battle replaced. Nature has willed that the Crustacean should not long remain an invalid. They soon return cured of their wounds. "We have seen lobsters," says Moquin-Tandon, "which have in an unfortunate rencounter lost a limb, sick and debilitated, reappear at the end of a few months with a perfect limb, vigorous, and ready for service. O Nature, how thou fillest our souls with astonishment and wonder!"

On the Spanish coast there is a species of crab, known, singularly enough, by the name of _Boccaccio_; it is caught for its claw, which is considered excellent eating. This is cut off, and the mutilated animal is thrown into the sea, to be taken at some future time when the claw has reappeared.

Crustaceans are nearly all carnivorous, and eat eagerly all other animals, whether living or dead, fresh or decomposed. Little think they of the quality or condition of their food. It is amusing to witness the address and gravity with which the common crab, when it has seized an unfortunate mussel, holds the valve open with one claw, while with the other it rapidly detaches the animal, carrying each morsel to the mouth, as one might do with the hand, until the shell is entirely empty. The crab does not kill its prey directly, like the lobster; it is swallowed also, but with greater appreciation.

M. Charles Lespés surprised upon the shore at Royan a shoal of crabs at their repast. This day they seem to have dined in common, and "God knows the enjoyment," as the good Fontaines said. They were in rows, every head turned to the same side, and nearly on end on their eight feet. They seized the small objects on the shore, which were carried to the mouth, each hand in its turn in regular order: when the right hand reached the mouth the left was on the ground. Let us just figure to oneself a company of disciplined soldiers messing together at the same table!

The Long-horned Corophius (_Corophium longicorne_), remarkable for its long antennæ, knows perfectly well how to cut the byssus by which the mussels suspend themselves, in order that the bivalve may fall on the weeds among them. Other Crustaceans, also great oyster-eaters, have the cunning or instinct to attack the mollusc without exposing themselves to danger. When the bivalve half opens its shell to enjoy the rays of the sun or take food, the evil-disposed Crustacean slips a stone between the valve. This done, it devours the poor inhabitant of the shell at its leisure.

The Corophius, respecting whom this question is hazarded, are extremely numerous on the shores of the Atlantic towards the end of summer and autumn. They make constant war upon certain marine worms. Off the coast of La Rochelle they may be seen in myriads beating the muddy bottom with their long antennæ in search of their prey. Sometimes they meet one of these Nereida or Arenicola many times their own size, when they unite in a body to attack it. In the oyster beds of La Rochelle they are useful friends to the oyster by destroying these enemies, although they do not hesitate to attack the mollusc when it comes in their way. During the winter the mud of the bouchots gets piled up in unequal heaps, and when the warm season returns, it has become hard and unfit for the cultivation of the mollusc. It is necessary to level and dry these mud-heaps--a process which would be both difficult and costly. Well, the Corophia charge themselves with the task. They plough up annually many square leagues covered with these heaps. They dilute the mud, which is carried out by the ebbing tide, and the surface of the bay is left smooth, as it was in the preceding autumn.

We have said that the Crustaceans do not even respect each other; the larger of the same species often devour the smaller. _Rara concordia fratrum!_ Mr. Rymer Jones relates that he had on one occasion introduced six crabs (_Platycarcinus pagurus_) of different size into an aquarium. One of them, venturing towards the middle of the reservoir, was immediately accosted by another a little larger, which took it with its claws as it might have taken a biscuit, and set about breaking its shell, and so found a way to its flesh. It dug its crooked claws into it with voluptuous enjoyment, appearing to pay no attention to the anger and jealousy of another of its companions, which was still stronger and as cruel, and advanced towards them. But, as Horace says--and he was not the first to say it--"No one is altogether happy in this lower world":

"Nihil est ab omni parte beatum."

Our ferocious Crustacean quietly continued its repast, when its companion seized it exactly as it had seized its prey, broke and tore it in the same fashion, penetrating to its middle, and tearing out its entrails in the same savage manner. In the mean time the victim, singularly enough, did not disturb itself for an instant, but continued to eat the first crab bit by bit, until it was itself entirely torn to pieces by its own executioner--a remarkable instance at once of insensibility to pain and of cruel infliction under the _lex talionis_. To eat and to be eaten seems to be one of the great laws of Nature.

Though essentially carnivorous, the Crustaceans sometimes eat marine vegetables. Many even seem to prefer fruit to animal food. Such is the robber-crab (_Birgus latro_) of the Polynesian Isles, which feeds almost exclusively on the cocoa-nut. This crab has thick and strong claws; the others are comparatively slender and weak. At first glance it seems impossible that it could penetrate a thick cocoa-nut surrounded by a thick bed of fibre and protected by its strong shell; but M. Liesk has often seen the operation. The crab begins by tearing off the fibre at the extremity where the fruit is, always choosing the right end. When this is removed, it strikes it with its great claws until it has made an opening; then, by the aid of its slender claws, and by turning itself round, it extracts the whole substance of the nut.

The Crustaceans have eyes of two kinds--simple and compound: the first are sessile and immovable, and very convex; the other borne on a short calcareous stem or peduncle, and formed of a number of small eyes symmetrically agglomerated--the reunion of all the microscopic cornea of a composite eye, resembling in shape a cap formed of facets. It is said, for instance, that the eye of the lobster consists of 2500 of these little facets. The simple eyes are _myopus_, or short-sighted--the compound eyes for more distant but perfect sight. They appear to have a strong sense of smell. Many of them cannot swim, but walk with more or less facility at the bottom of the water. It is said, for instance, that the cavalier of the Syrian coast, _Oxypoda cursor_ (Fabricius), is named from the rapidity with which it traverses great distances.

Many systems have been proposed by different writers for the arrangement of the Crustacea. That proposed by Mr. Milne Edwards recommends itself, being founded on anatomical examination and actual experiment made by himself and M. Audouin. He divides them into two great divisions: I. Those in which the mouth is furnished with a certain number of organs adapted for the prehension or division of food. II. Those in which the mouth is surrounded by ambulatory extremities, the bases of which perform the part of jaws. The first includes the MAXILOSA or MANDIBULATA, again divided into _Decapoda_, having branchiæ attached to the sides of the thorax, and enclosed in special cavities. The _Decapoda_ are divided into: 1. BRACHYURA, namely, the Crabs. _Cancer_, _Porlunus_, _Grapsus_, _Ocypode_, and _Doippe_, belong to this group. 2. ANOMOURA, including _Droma_, _Pagurus_, _Porcellana_, and _Hippa_. 3. MACROURA, including the Lobsters, _Astacus_, _Palæmon_, the Craw-fish, _Palinurus_.

_Stomatopoda_, with external branchiæ, sometimes rudimentary, sometimes none. Thoracic extremities prehensile, or for swimming generally, six or eight pairs. This division includes Mysids, Phyllosoma, Squilla, &c.

The Cirripedia, or barnacles, are a very important division of Crustacea; they are found in all seas, and attach themselves to almost every object in the sea; from the immovable rock to the moving animal; from the little Tunicata to the great turtle, or the whale.

The goose barnacles, _Anatifa_, have a flexible peduncle. The Balanoidea, or sea acorns, like oysters, are rooted to the spot on which they rest in their infant days; without the power, like the goose barnacle, of swaying to and fro like a pendulum, be their resting-place what it may.

One of the most remarkable animals of this class of Crustacea is the _Limulus Moluccanus_--the Molucca crab. They are distinguished by a long serrated spine, which looks most formidable. They are in great request in the markets of Java. Linnæus thought that the fossil trilobites were closely allied to the _Limulus_. Latreille, on the contrary, classed them near the mollusc, chiton. The tail of _Limulus_ so strikingly resembles that of many Trilobites, that the most common observers may perceive an affinity.

CRABS AND CRAW-FISH.

Crabs and lobsters may be regarded as the chiefs or lords of the Crustacean tribes. The crabs have very large claws and smooth backs; the last have small claws and the back covered with spines. Tiberius Cæsar had the face of a poor fisherman scratched by the rugged shell of a craw-fish.

Lobsters, especially, have an amazing fecundity, and yield an immense number of eggs, each female producing from 12,000 to 20,000 in the season. The crab is also very prolific. These eggs are, in the lobster, arranged in packets, which are attached to the lower surface of the tail, to which they are connected by a viscous substance. The manner in which the female lobster disposes of her burden is curious and interesting. Whether she bends or stands erect she is able to hold it obscurely or expose it to the light. Sometimes, according to Coste, the eggs are left immovable, or simply submerged; at others they are subjected to successive washings by gently agitating the false claw which shelters them from right to left. When first exuded from the ovary the eggs are very small, but they seem to increase during the time they are borne about under the tail, and before they are committed to the sand or water they have attained the size of small shot. The evolution of the germ is in progress during six months. At the moment of exclusion the female extends the tail, impresses upon the eggs an oscillating motion, in order to destroy the shell and scatter the larvæ, delivering herself in two or three days of her entire burden (Coste). "As the young lie enclosed within the membrane of the egg," says Couch, "the claws are folded on each other, and the tail is flexed on them as far as the margin of the shield. The dorsal spine is bent backwards, and lies in contact with the dorsal shield, for the young when it escapes from the egg is quite soft; but it rapidly hardens and solidifies by the deposition of calcareous matter on what may be called its skin."

As soon as born, the young Crustaceans withdraw from the mother and ascend to the surface of the water, in order to gain the open sea. They swim in a circle; but this pelagic life is not of long duration; they quit it after their fourth moult, which takes place between the thirtieth and fortieth day, at which time they lose the transitory organs of natation which they have hitherto possessed. After this they are no longer able to maintain themselves on the surface, but drop to the bottom. Henceforth they are condemned to remain there, and such walking as they can exercise becomes their habitual mode of progression. As they increase in size they gradually approach the shore, which they had for the moment abandoned, and return to the places inhabited by the parent Crustaceans.

The form of the larvæ differs so much from that of the adult, that it would be difficult, except on the clearest evidence, to determine the species from which they proceed. Former naturalists considered the embryo cray-fish (_Palinurus_) to belong to a distinct genera, which they designated _Phyllosoma_. It is now known, however, that these are the young of the higher forms of Crustaceans undergoing metamorphosis. In the various forms of _Macroura_ the metamorphosis is less decided than in the _Brachyura_. In the fresh-water cray-fish no change whatever takes place. Dissatisfied with the uncertainty of former experiments, Mr. Couch undertook a series of observations, which are recorded in the proceedings of the Cornwall Polytechnic Society, in which he established the fact that metamorphosis takes place in the following genera: Cancer, Xanthò, Plumnus, Carcinus, Portunus, Maja, Galathea, Hornarus, and Palinurus. "Metamorphosis has been demonstrated," says Dr. Bell, "in no less than seventeen genera of the Brachyurous order of Decapoda, in which it is most decided and obvious; in Leptopodia, Majacea, Cancer, Portunidæ, Pinnoteres, and Grapsus. In the Anomourous order it is seen in the Pagurus, Porcellana, and Galathea; and in the Macrouran order in Homarus, Palinurus, Palæmon, and Crangon."

The swimming of these creatures is produced by flexions and expansions of the tail, and by repeated beating motions of the claws, the tail acting as a sort of vibratile oar, aided by which they maintain themselves in the water and facilitate their progress. As the shell becomes more solid they get less active, and finally return to the bottom to cast their shell and assume a new form.

According to the observations of M. Coste, the young lobster casts its shell from eight to ten times in the first year, from five to seven in the second, three to four times the third, and two or three times the fourth year. In the fifth year they attain the adult state. Whence it follows, that the small lobsters served at our tables have changed their calcareous vestment something like twenty-one times, and are now clothed in their twenty-second habit.

The crabs are numerous in species and various in size. The long-clawed crab (_Corystes Cassivelaunus_) of Pennant and Leach (Fig. 335) is remarkable for its long antennæ, which considerably exceed the body. The jaw-feet have their third joint longer than the second, terminating in an obtuse point, with a notch on its interior edge; eyes wide apart, borne upon large peduncles, which are nearly cylindrical and short; anterior feet large, equal, twice the length of the body, and nearly cylindrical in the males; in the females (Fig. 336) about the length of the body, and compressed, especially towards the hand-claw. The other feet terminate in an elongated nail or claw, which is straight-pointed and channeled longitudinally: carapace oblong-oval, terminating in a rostrum anteriorly truncated and bordered posteriorly; the regions but slightly indicated, with the exception of the cordian region, the branchial or lateral regions being very much elongated.

Latreille gives the name of Corystes, which signifies a warrior armed, to this genus of Crustaceans, from κόρυς, a helmet, but it is perfectly inoffensive. Pennant had already conferred the name of _Cassivelaunus_, the chief of the Ancient Britons, for the singular reason, according to Gosse, that the carapace, which is marked by wrinkles, bears, in old males especially, the strongest and most ludicrous resemblance to the face of an ancient man. Pennant's well-known sympathy with his British ancestry certainly never led him to caricature the grand old British warrior, as Mr. Gosse surmises. On the contrary, he saw in the Crustacean a creature armed at all points, and he named it after the hero of his imagination.

In this species the surface of the carapace is somewhat granulous, with two denticles between the eyes, and three sharp points directed forward on each side. The male has only five abdominal pieces, but the vestiges of the separation of the two others may be clearly remarked upon the outer mediate or third piece, which is the largest of all. The length of the antennæ is remarked on by Mr. Couch, in his Cornish Fauna. "These organs," he says, "are of some use beyond their common office of feelers; perhaps, as in some other Crustaceans, they assist in the process of excavation; and, when soiled by labour, I have seen the crab effect their cleaning by alternately bending the joints of their stalks, which stand conveniently angular for the purpose. Each of the long antennæ is thus drawn along the brush that fringes the internal face of the other, until both are cleared of every particle that adhered to them." On the other hand, Mr. Gosse suggests that the office of the antennæ is to keep a passage open for ejecting the deteriorated water after it has bathed and aerated the gills. "I have observed," he says, "that, when kept in an aquarium, these crabs are fond of sitting bolt upright, the antennæ placed close together, and pointing straight upwards from the head. This is doubtless the attitude in which the animal sits in its burrow, for the tips of the antennæ may often be seen just projecting from the sand. When the chosen seat has happened to be so close to the glass side of the tank as to bring the antennæ within the range of a pocket lens, I have minutely investigated these organs without disturbing the old warrior in his meditation. I saw on each occasion that a strong current of water was continuously pouring up from the points of the antennæ. Tracing this to its origin, it became evident that it was produced by the rapid vibration of the foot-jaws drawing in the surrounding water, and pouring it off upwards _between the united antennæ_, as through a tube. Then, on examining these organs, I perceived that the form and arrangement of their bristles did indeed constitute each antennæ a semi-tube, so that when the pair were brought face to face the tube was complete."

Among the numerous genera of _Brachyurous Crustaceans_, Grapsus is distinguished by its less regularly quadrilateral form; the body nearly always compressed, and the sternal plastron but little or not at all curved backwards; the front strongly recurved, or, rather, bent downwards; the orbits oval-shaped and of moderate size; the lateral edges of the carapace slightly curving and trenchant; the ocular pedicles large, but short: their insertion beneath the front and the cornea occupies one-half of their length.

The Hermit or Soldier Crab (_Pagurus Bernhardus_, Fabricius, Fig. 337) is, perhaps, the oddest and most curious of Crustaceans. It differs from most other Crustaceans in this: in place of having the body protected by a calcareous armour, more or less thick and solid, it has only a cuirass and head-piece to protect the head and breast; all the rest of the body is invested in a soft yielding skin; and this, the vulnerable part of the hermit crab, is the delicate morsel devoured by the gourmet. Nor is our somewhat evil-disposed Crustacean ignorant of the perfectly weak and defenceless state of its posterior quarters. Prudence or instinct makes it seek the shelter of some empty shell, of a shape and size corresponding to its own. When it fails to find one empty, it does not hesitate to attack some living testacean, which it kills without pity or remorse, and takes possession of its habitation without other form of process. Once master of the shell (Fig. 337), it introduces itself, stern foremost, and installs itself as in an entrenchment, where it is established so firmly that it moves about with it more or less briskly, according to its comparative size.

The Pagurians belong to the Anomourous family of Crustaceans, of which there are several genera, and a considerable number of species, the animal economy of which has been ably commented upon by Mr. Broderip. "Their backs," he says, "are towards the arch of the turbinated shell occupied by them, and their well-armed nippers and first two pairs of succeeding feet generally project beyond the mouth of it. The short feet rest upon the polished surface of the columella, and the outer surface of their termination, especially that of the first pair, is in some species most admirably rough-shod, to give 'the soldier' a firm footing when he makes his sortie, or to add to the resistance of the crustaceous holders at the end of his abdomen, or tail, when he is attacked, and wishes to withdraw into his castle. On passing the finger downwards over the terminations of these feet, they feel smooth; but if the finger be passed upwards, the roughness is instantly perceived. The same sort of structure (it is as rough as a file) is to be seen in the smaller caudal holders." In another species of Pagurus, from the Mauritius, which was nearly a foot in length, he found a great number of transverse rows, armed with acetabula, or suckers; these were visible without the aid of a glass, which must very much assist the hold of the _Pagurus_.

During the feeding and breeding-time, the hermit throws out his head and feet, and especially his great claws, and feels his way with his two antennæ, which are long and slender. When he walks he hooks on with his pincers to the nearest body, and draws his shell after him, as the snail does his. But the undefended parts of the body always remain under cover. At low water the hermits spread themselves over the rocky shore, and the spectator thinks he sees a great number of shells which move in all directions, with allurements different from that which belongs to their essentially slow and measured race. If they are touched they stop suddenly, and it is soon discovered that their shell is the dwelling of a crustacean, not a mollusc. The animal lives alone in its little citadel, like the hermit in his cell or the sentinel in his box. Hence the name of _hermit_ and _soldier_.

When our crustacean outgrows its borrowed habitation, it sets out in search of another shell, a little larger, and better suited for its increased size.

The hermit often avails itself, as we have said, of empty shells abandoned by their owners; when the tide retires these seldom fail them, and the hermit may be seen examining, turning, and returning, and even trying its new domicile. It glides slowly along on its abdomen, which is large and somewhat distorted, sometimes in one shell, sometimes in another, looking defiantly all round it, and returning very quickly to its ancient lodging if the new one does not turn out to be perfectly comfortable, often trying a great number, as a man might try many new clothes before suiting himself. In its successive removals the little sybarite chooses a hermitage more and more spacious, according to its taste or caprice in colour or architecture. The cunning little creature chooses its mansion, now grey or yellow, now red or brown, globular or cylindrical, in the form of a spiral or of a tun, toothed or crenulate, with trenchant edge or pointed terminations; but, as a rule, our crustacean Diogenes houses itself in spirals of considerable length, as in _Cerithium_, _Buccinum_, or _Murex_.

The hermit is very timid; at the least noise it shrinks into its shell and squats itself, without motion, drawing in its smaller claws and closing the door with its larger ones, the latter being often covered with hairs, tubercles, or with teeth. In short, our prudent cenobite clings so closely to the bottom of its retreat, that we might pull it to pieces without getting it out entire; its tail is transformed into a sort of sucker, by the aid of which it attaches itself firmly to the walls of its habitation. It is at once strong and voracious, eating with much relish the dead fishes and fragments of molluscs and annelids which come in its way. Nor does it hesitate to attack and devour living animals. When introduced into an aquarium, it has sometimes thrown it into the utmost disorder by its insatiable rapacity. It has been possible sometimes to preserve harmony among many individuals inhabiting the same reservoir; but this has been owing rather to the impossibility of their attacking each other, in consequence of cunningly-devised barricades, than to their mildness of character or love of their neighbour. These animals, in short, are very quarrelsome. Two hermits cannot meet without showing hostility; each extends his long pincers, and seems to try to touch the other, much as a spider does when it seeks to seize a fly on its most vulnerable side; but each, finding the other armed in proof, and perfectly protected, though eager to fight, usually adopts the better part of valour, and prudently withdraws. They often have true passages of arms, nevertheless, in which claws are spread out, and displayed in the most threatening manner; the two adversaries tumbling head over heels, and rolling one upon the other, but they get more frightened than hurt. Nevertheless, Mr. Gosse once witnessed a struggle which had a more tragic end. A hermit crab met a brother Bernhard pleasantly lodged in a shell much more spacious than his own. He seized it by the head with his powerful claws, tore it from its asylum with the speed of lightning, and took its place not less promptly, leaving the dispossessed unfortunate struggling on the sand in convulsions of agony. "Our battles," says Charles Bonnet, "have rarely such important objects in view: they fight each other for a house."

A pretty little zoophyte, the Cloak Anemone (_Adamsia palliata_), loves to live with the hermit, and exhibits sympathies almost inexplicable. In aquariums this anemone attaches itself almost always to the shell which serves as the dwelling of the Crustacean; and it may be looked upon as certain that where the hermit is there will the anemone be found. These two creatures seem to live in perfect and intelligent harmony together, for Mr. Gosse's observations establish the existence of a cordial and reciprocal affection between them. This learned and intelligent observer describes the proceedings of a hermit which required a new habitation; he saw it detach, in the most deliberate but effective manner, its dear companion, the anemone, from the old shell, transport it with every care and precaution, and place it comfortably upon the new shell, and then with its large pincers give to its well-beloved many little taps, as if to fix it there the more quickly. Another species of Bernhardus makes a companion of the _mantled anemone_. "And we are assured," says Moquin-Tandon, "that when the crab dies its inconsolable friend is not long in succumbing also."

"Is there not here much more than what our modern physiologists call automatic movements, the results of reflex sensorial action?" says Gosse. "The more I study the lower animals, the more firmly am I persuaded of the existence in them of psychical faculties, such as consciousness, intelligence, skill, and choice; and _that_ even in those forms in which as yet no nervous centres have been detected."

LOBSTERS.

In a dietary, as well as commercial sense, the lobster far excels the crab; like the latter, they have an amazing fecundity, each female producing from twelve to twenty thousand eggs in a season; and wisely is it so arranged, otherwise the consumption would soon exhaust them.

In France the size of the marketable lobster is regulated by law, and fixed at twenty centimètres (eight inches) in length; all under that size are contraband. Every year the inhabitants of Blainville proceed to Chaussey to fish for lobsters. They are taken in baskets in the form of a truncated cone, the mouth of which is so arranged that the animal can enter, but cannot get out. The numbers caught by each fisherman and his family in a season may be estimated at a thousand or twelve hundred, which realise to the family thirteen or fourteen hundred francs, the season lasting about nine months.

Lobsters are collected all round our own coast for the London market. On the Scottish shore they are collected and kept in perforated chests floating on the water, until they can be taken away to market. From the Sutherland coast alone six to eight thousand lobsters are collected in a season. This process goes on all round the coast, and as far as Norway, whence an enormous supply of the finest lobsters are obtained, for which something like £20,000 per annum is paid, all these contributions being conveyed to the Thames and Mersey in welled vessels. But these old-fashioned systems are being rapidly superseded by the construction of artificial storing ponds, or basins. Of these ponds Mr. Richard Scovell has erected one at Hamble, near Southampton, in which he can store with ease fifty thousand lobsters, which will keep in good condition for six weeks. Mr. Scovell's tank is supplied from the coasts of France, Scotland, and Ireland, where fine lobsters abound. He employs three large and well-appointed smacks, each of which can carry from five thousand to ten thousand. On the coast of Ireland alone, it is said, ten thousand fine lobsters a week might be taken.

The Lobster (_Homarus_) is found in great abundance all round our coast; frequenting the more rocky shores and clear water, where it is of no great depth, about the time of depositing its eggs. Various are the modes in which they are taken; cone-shaped traps made of wicker-work, and baited with garbage, are perhaps the most successful. These are sunk among the rocks, and marked by buoys. Sometimes nets are sunk, baited by the same material. In other places a wooden instrument, which acts like a pair of tongs, is used for their capture.

Mr. Pennant, the naturalist, paid great attention to the lobsters, and their habits are well described in a letter from Mr. Travis, of Scarborough. "The larger ones," he says, "are in their best season from the middle of October to the beginning of May. Many of the smaller ones, and some few of the larger individuals, are good all the summer. If they are four and a half inches long from the top of the head to the end of the back shell, they are called sizeable lobsters; if under four inches, they are esteemed half size, and two of them are reckoned for one of size. Under four inches they are called pawks, and these are the best summer lobsters. The pincers of one of the lobster's large claws are furnished with knobs, while the other claw is always serrated. With the former it keeps firm hold of the stalks of submarine plants; with the latter it cuts and masticates its food very dexterously. The knobbed or thumb claw, as the fishermen call it, is sometimes on the left, sometimes on the right side, and it is more dangerous to be seized by the serrated claw than the other."

There is little doubt that the lobsters cast their shell annually, but the mode in which it is performed is not satisfactorily explained. It is supposed that the old shell is cast, and that the animal retires to some lurking-place till the new covering acquires consistence to contend with his armour-clad congeners. Others contend that the process is one of absorption, otherwise, if there were a period of moult, it would be shown by their shells. The most probable conjecture is that the shell sloughs off piecemeal, as it does in the cray-fish. The greatest mystery of all, perhaps, is the process by which the lobster withdraws the fleshy part of its claws from their calcareous covering. Fishermen say the lobster pines before casting its shell, so as to permit of its withdrawing its members from it.

The female lobster does not seem to cast her shell the same year in which she deposits her ova, or, as the fishermen say, "is in berry." When the ova first appear under the tail, they are small and very black, but before they are ready for deposition they are almost as large as ripe elderberries, and of a dark-brown colour. There does not seem to be any particular season for this act, as females are found in berry at all seasons, but more commonly in winter. In this state they are found to be much exhausted, and by no means fit for the table.

The generic name, _Astacus_ of Fabricius, is now confined to the crawfishes, which have a depressed rostrum, one tooth on each side, and the last ring of the thorax movable. The lobsters (_Homarus_) have the eyes spherical, two rings of the thorax being soldered together. The Norway Lobsters (_Nephrops Norvegicus_, Fig. 338) have the eyes uniform, and the two last rings of the thorax movable.

The last is one of the most beautiful of the larger Macrourans. Its general tint is pale flesh colour, with darker shades in parts, its pubescence light brown. This is generally considered a northern species, but Mr. Bell states that he has received specimens from the Mediterranean. It is found plentifully on the coast of Norway, on the Scottish coast, and in the Bay of Dublin. It is considered the most delicate of all the Crustaceans.

Before concluding this chapter, we perhaps should not omit brief notices of the common prawn (_Palæmon serratus_) and the shrimp (_Crangon vulgaris_), as types of an extensive variety of form of crustacea, which inhabit all seas, and which perform important functions as regards the sanitary state and economic condition of the waters of the ocean. These small animals are the scavengers of the sea--they pick up and devour all dead matter, leaving (it may be) a clean skeleton, without a shred of fibre behind. In this respect they resemble the ants on land, doing their work always thoroughly and effectively. We need hardly mention, what is so well known to every reader, that prawns and shrimps are amongst the most esteemed delicacies at our table, and as articles of food occupy no mean place on the fish-stall. At Billingsgate alone, it is hardly credible the immense quantities which arrive and are daily consumed in the Metropolis by all classes of the community. The shrimp, which although the smaller crustacean, is perhaps the finest flavoured of the two, is sold in much larger quantities than its more aristocratic congener, the prawn. The fishery of these savoury comestibles gives occupation not only to regular able-bodied fishermen, who devote themselves to this branch, but also to large numbers of women and children, who--with their baskets and small nets--may be seen plying their vocation in a multitude of well-known localities on our coasts, especially on the southern and south-eastern shores. To the habitués of Hastings, Southampton, Bognor, &c., there is not a more picturesque or familiar marine picture than to behold a troop of little shrimpers, in their grotesque and somewhat outré equipments, wading patiently knee deep all in a row, as they push before them their pole nets.

Without giving a detailed technical and anatomical description, which our space will not permit of, we may observe that the common prawn (_Palæmon serratus_) is about four or five inches long, with a rounded carapace, which is jointed and furnished at the head with numerous long antennæ, the eyes being large and round. The tail is broad and flat, the caudal laminæ of which are furnished with long hairs on the terminal margins. The animal is also furnished with several pairs of feet, very slender, and ordinarily bent within themselves.

The colour is light grey, spotted and lined with purplish shades. In the water, however, prawns are almost transparent, from the nearly entire absence of carbonate of lime in the carapace; they are thus very beautiful objects in the marine aquarium, moving as they do like shadows in the water.

When prawns are boiled, they become of a delicate pink colour, thus adding beauty to the dainty morceaux.

Like most other kinds of crustacea, the prawn is much larger in tropical climates. On the coast of South America, for instance, they attain a size of nine or ten inches in length, three of them being considered quite sufficient for a meal.

The London market is chiefly supplied with prawns from the Isle of Wight and Hampshire coast.

Like the prawn, the shrimp has many varieties. The common shrimp (_Crangon vulgaris_) is about two and a half inches long, from the eye to the extremity of the tail. It is also furnished with a rounded articulated carapace, with two antennæ. The eyes are prominent, marked, and near each other; the tail flat, laminated, and hirsute. The shrimp is not very unlike the prawn in general appearance, but is of a much less complex and finished structure.

In colour it is greyish brown, clotted all over with dark brown. In this species heat does not improve the colour.

This variety is one of the most abundant of all coast crustacea, swimming about and laying on the sands (which they closely resemble in colour) in immense shoals. Sometimes they are also found in deep water, but the margin of the sea is their favourite habitat. It may be added, that large quantities of the smaller palæmonidæ are caught with and sold as shrimps. Shrimps are in spawn all the year through, and cast their shells during the three months of spring.

The _Entomostraca_ of Milne Edwards, or the _Lophyropoda_ of Latreille, have no suctorial mouth or mandibles capable of mastication; their maxillæ are lamellose, and they have never more than ten swimming feet, and have from one to two eyes on stalks, and live in fresh water. There are two principal genera; the _Copepoda_ of Edwards, and the _Ostracoda_. As a type of the first, we may mention _Cyclops vulgaris_ (Leach), which, true to its name, has but one eye. But the genus _Pontia_ of the same family has two. As a type of the second order, _Ostracoda_, we will specify the numerous family of the _Cyprides_, whose animals are enclosed in a bivalve shell, which causes their remains in Secondary strata to be classed with bivalve molluscs.