Strange as are these habits, there is still a kind of analogy with other modes of animal life. On page 625 is mentioned the curious little crustacean which resides within the body of a beroë, and in the present instance there is an evident analogy with the various galls and their inhabitants, the cells of the Phoxichilidium being in fact the galls of the coryne.

THE crustacea abound in strange forms. The LONG-TAILED MOLUCCA CRAB belongs to a separate order, called by the name of Xiphosúra, or Sword-tailed Crustacea, in allusion to the long and sharp spine which projects from the shell. These creatures, of which several species are known, can easily be recognised by their general shape. The body and limbs are covered by a curious shield composed of two parts, the junction taking place across the centre of the body, as may be seen by reference to the engraving. Though perfectly harmless, these creatures can be made very offensive, for the natives of Molucca are accustomed to use the long sharp tail spine as the head for an arrow or lance, and thus make a most formidable weapon. Many of these crustacea attain the length of two feet, so that the spike is nearly a foot in length, and is capable of inflicting a deadly wound.

The edges of the hinder portion of the shield are deeply toothed, and the space between each tooth is occupied by a rather long and sharply pointed spine, which is not fixed, but is moveable on its basis. The feet are mostly furnished with tolerably strong claws.

The Molucca Crabs often leave the sea and crawl upon the sand, where they may be taken without much difficulty. They cannot endure the heat of the sun's rays, and are

in the habit of burrowing into the sand when the sunbeams beat too fiercely on their shells. Sometimes they do not bury themselves very deeply, and then they are discovered by the projecting tail spike, which shows itself above the level of the sand, and betrays the position of the animal. As they pass over the sand they present a very curious appearance, as their large shield-like shell entirely covers the limbs, and the creatures seem to be carried along by some external agency rather than to be propelled on their own limbs. Owing to the shortness of the legs, and the large rounded shell, the Molucca Crabs are almost helpless if laid on their backs, being obliged to wait until some friendly wave may strike them and enable them to resume their proper attitude. These crustaceans occur largely in certain strata, and are found in a fossil state, many species attaining to a very great size. One living species (Limulus cyclops) is a native of the East Indies, and goes by the popular name of PAN-FISH, or SAUCEPAN-CRAB, because the shell, when the limbs and body have been removed and the tail spine permitted to retain its place, has some resemblance to the useful culinary article from which it derives its name. It is often used as a ladle for dipping water out of a vessel.

WE now come to the last members of the crustacea, creatures which were for a long time placed among the molluscs, and whose true position has only been discovered in comparatively later years. Popularly they are called Barnacles, but are known to naturalists under the general term cirrhipedes, on account of the cirrhi, or bristles, with which their strangely transformed feet are fringed.

When adult, all the cirrhipedes are affixed to some substance, being either set directly upon it, as the common acorn barnacle, so plentiful on our coasts; placed upon a footstalk of variable length, as in the ordinary goose-mussel; or even sunk into the supporting substance, as is the case with the whale barnacles. When young, the cirrhipedes are free and able to swim about, and are of a shape so totally different to that which they afterwards assume, that they would not be recognised except by a practised eye. More will be said on this subject.

Along the under surface are set six pairs of limbs not furnished with claws, but being developed at their extremities into two long filaments, jointed and covered with hairs. By means of these modified limbs the cirrhipedes obtain their food. The common acornbarnacle of our coasts affords a familiar and beautiful example of the mode by which this structure is made subservient to procuring supply of food. The closed valves at the upper part of the shell are seen to open slightly, a kind of fairy-like hand is thrust out, the fingers expanded, a grasp made at the water, and the closed member then withdrawn. into the shell.

This hand-like object is in fact the aggregated mass of legs with their filaments. As the limbs are thrust forward, they spread so as to form a kind of casting net; and as they return to the shell, they bring with them all the minute organisms which were swimming in the water. This movement continues without cessation, as long as the Barnacles are covered with water, and appears to be as mechanically performed as the action of breathing as performed by the higher animals.

We will now cast a hasty glance at the transformations through which these creatures pass before attaining their perfect state. It has already been mentioned that the young cirrhipedes are free and able to wander about at will; and as is generally the case in such instances, they are apparently of a higher organization when young than when adult. For example, the young Barnacle can swim freely with certain limbs. When adult, it loses those limbs. When it is young, it possesses eyes; but when it attains maturity, it loses those valuable organs, which, although indispensable to a wanderer, are needless for a being which is fixed to one spot and needs not to move in order to obtain subsistence.

When first set free from the parent, the Barnacle is extremely minute, and has a striking resemblance to the young of one of the Entomostraca already described. It has three pairs of legs, with imperfect joints and ending in bristle-like appendages. By the vigorous flapping of these limbs the young Barnacle is driven quickly through the water, with a sharp but uncertain movement. In fact, a microscope of low power, when applied

646

THE GOOSE-MUSSEL OR DUCK-BARNACLE.

to the water wherein a number of these tiny creatures are swimming, discloses a swarm of merry little beings playing about just like the clouds of gnats over water, or the dancing motes in the sunbeam.

Just in the middle of the part of the body which by courtesy we will call the forehead, a single eye is placed, black, round, and shining as if it were a little jet bead inserted into the body. There are also two very large antennæ, which serve two useful purposes, for they aid the free and imperfect Barnacles to proceed through the water, while they are the means whereby the creature fixes itself to the rock when about to undergo its last change.

It then passes through a series of changes, casting off its skin at every change, and exhibiting the curious phenomenon that, in its form and general appearance, it presents a strange resemblance to the young of several Entomostraca, such as cypris and cyclops. When it is ready for the final change, the young Barnacle seeks some rock or other resting-place, and begins operations by pressing the large antennæ against the supporting substance. A curious cement or glue is then poured from their bases: as this cement is not soluble in water, it fixes the creature firmly to the rock. Almost as soon as it is fairly settled, the Barnacle again casts its skin, parting with the bivalve shell which guarded its body, casting away the eye which has hitherto directed its_course, and assumes, though still of very minute form, the shape of the adult.

After describing these wonderful changes, Mr. Gosse makes the following apt remark. "Marvellous indeed are these facts. If such changes as these, or anything like them, took place in the history of some familiar domestic animal-if the horse, for instance, were invariably born under the shape of a fish, passed through several modifications of this form, imitating the shape of the perch, then the pike, then the eel, by successive casting off its skin; then by another shift appeared as a bird, and then, gluing itself by its forehead to some stone, with its feet in the air, threw off its covering once more and became a foal, which then gradually grew into a horse;—or if some veracious traveller, some Livingstone or Barth, were to tell us that such processes were the invariable conditions under which some beast of burden largely used in the centre of Africa passed; should we not think them very wonderful? Yet they would not be a whit more wonderful in this supposed case than in the case of the Barnacle, in whose history they are constantly exhibited in millions of individuals and have been for ages and even in creatures so common that we cannot take a walk beneath our sea cliffs without treading on them by hundreds."

Having thus glanced cursorily at the general structure and habits of the cirrhipedes, we will proceed to the individual specimens which are figured in the illustration.

IN the upper left-hand corner of the illustration is seen a group of the common GOOSE-MUSSEL or DUCK-BARNACLE, so called on account of the absurd idea that was once so widely entertained, that this species of barnacle was the preliminary state of the barnacle-goose, the cirrhi representing the plumage, and the valves doing duty for the wings.

This Barnacle is tolerably universal in its tastes. It clings to anything, whether still or moving, and is the pest of ships on account of the pertinacity with which it adheres to their planks. Its growth is marvellously rapid, and in a very short time a vessel will have the whole of the submerged surface coated so thickly with these cirrhipedes that her rate of speed is sadly diminished by the friction of their loose bodies against the water

When once the Goose-mussel has affixed itself to any object, the rapidity of its growth is positively startling. The minute young are poured from its shells in such multitudes that they look like cloudy currents in the water; and after they have enjoyed their brief period of freedom, they settle down, attain maturity, and in their turn become the origin of a countless posterity.

I have seen a large log of timber, about fourteen feet in length by one foot square, so thickly covered with these Barnacles that the wood on which they rested was not visible. The same log, which had evidently formed part of the cargo of a timber ship,

had been attacked by the ship-worm as well as the Barnacle, and had been tunnelled from end to end by that insatiable devourer. The log was so entirely covered by the Barnacle and the shipworm, that the wood of which the beam was composed was quite

648

THE PARROT'S-BEAK BARNACLE.

invisible, and could not be seen until the heavy masses of Barnacles were lifted up by the hand.

The old boatman who had picked up the log while fishing, and had ingeniously built a trough to receive the log, a tank of sea water to supply the trough, and a kind of tent composed of sails to hold the trough and the log together, was very full of a discovery that he had made. He was fully persuaded that the ship-worm and the Barnacle were identical, and that when the ship-worm was tired of boring into wood, it came to the surface, and was immediately changed into a Barnacle. He was quite impervious to reason, and always went into a passion whenever the facts seemed to contradict his theory.

If the objects were enumerated to which the Barnacle will cling, a volume would hardly be sufficient for the mere catalogue. It has been found on ships, boats, floating timber, shells, turtles, whales, and marine snakes. A moment is sufficient to give them a firm hold of any object, and when once they have fixed their antennæ, the fiercest storm cannot shake them off. Even after death, the force with which they cling is as great as during life, and they seem almost to form part of the substance to which it adheres. The length of the foot-stalk is extremely variable, in some measuring three or four times the length that it does in others. This species is found in nearly all temperate and

warm seas.

A second but smaller group of Stalked Barnacles is seen in the corresponding righthand corner. This is the FASCINE-BARNACLE, a larger and finer species, which, as may be seen by reference to the illustration, can be distinguished by the number and shape of its shelly valves. These valves, indeed, afford most important indications of the genus to which any species belongs, and in the arrangements of some zoologists they play the principal part in the formation of the system.

I may here mention that the whole of the figures upon the preceding illustration are drawn from specimens in the splendid collection of H. Cuming, Esq., who kindly lent them for the purpose, as were several of the more curious molluscous shells, such as the Chinese Pearl-mussel, shown on page 428. The same specimens were employed by Mr. Darwin in his elaborate work upon the cirrhipedes. The Fascine-barnacle is found in the Indian Ocean.

A rather singular form of Barnacle is seen just below the Goose-mussel, resting on short footstalks, and having somewhat triangular valves. This is the MITELLA-BARNACLE, which may be known by the stoutly shaped footstalks and the rough, shagreen-like character of their surface. At the base of the shell are seen a number of smaller accessory pieces, all pointed and marked with slight transverse lines. This species comes from China, the Philippines, &c.

Exactly in the centre of the illustration is placed a specimen of the EARED BARNACLE, which derives its appropriate name from the curious tubular projections which stand out boldly from either side, like the ears of a quadruped from the head. This species lives in the warmer seas.

A group of Eared Barnacles have been found attached to another genus of Barnacle, which lives on, or rather in, the skins of cetacea, and to which we shall presently allude. Indeed, these beings seem to care little about the substance to which they adhere, one species of Stalked Barnacle having actually been taken upon the delicate surface of a living Medusa.

We now leave the stalked barnacles, and proceed to those species which are placed directly upon the substances to which they adhere. A little to the right of the eared barnacle is seen a small group of upright shells, surrounded by buttress-like and pointed projections. This is the BELL-BARNACLE, found off the coast of Madeira, Africa, and other hot parts of the ocean. It sometimes attains a very considerable size, and is eaten by the Chinese, who think that it resembles the lobster in flavour.

Other species are also eaten, such as the PARROT'S-BEAK BARNACLE, a creature deriving its name from a curved projection something like the bill of a parrot. This enormous Barnacle is sometimes found measuring between five and six inches in height, and between three and four inches in diameter. It is found in large bunches, sometimes consisting of a hundred individuals, some adhering to the rocks and others to the shells of