Some of these animals, however, have been kept for months in a vessel of water, without apparent food, and in perfect health and vigour. The skin is of a pale flesh colour; but when the proteus is removed from its native situation, and exposed to light, it assumes a darker tint, approaching olive brown, and the branchial tufts become deeper. But the light is evidently distressing, and the animals are glad to creep beneath the shelter of any substance that may be near.

*

In another genus, the body is moderately elongated; the tail deep, and flattened at the sides; the head flat, and the branchial tufts large.

THE AXOLOTL. †

AT the period of the Mexican conquest, the Spaniards found this animal in great abundance in the lake which surrounded the city of Mexico, to the inhabitants of which capital it then furnished, as it still continues to furnish to their successors, an agreeable and much-esteemed article of food. When full grown, it measures about eight or nine inches in length; its ground colour is a uniform deep brown, thickly mottled both on the upper and under surfaces of the head and body, as well as the limbs, tail, and dorsal and caudal fins, with numerous small, round, black spots,

THE SIRENS.

We have now arrived at the last genus of reptiles, in which there are several species. One of these § grows to the length of three feet; its colour is blackish. The feet have four toes, and the tail is compressed into an obtuse fin.

This siren inhabits the marshy grounds of Carolina, especially those where rice is cultivated. It lives in the mud, from whence it makes excursions, sometimes on land, and sometimes in the water. Its food is generally supposed to consist of insects, earth-worms, &c. Specimens have occasionally been kept in the Zoological Gardens. One of these was twenty inches long, as large as the wrist of a stout child six months old, and very eel-like in its appearance and movements. It was kept in a vessel of pond-water, with a deep bottom of mud, in which it used to hide itself. About a dozen and a half of earth-worms were supplied to it as food every other day.

Dr. Patrick Neill, of Edinburgh, possessed one of these creatures. It measured one foot five inches in length, and about four inches in circumference. Its colour was deep blackish-brown, rather paler beneath, where it was partially tinged with a bluish hue; and marked all over with numerous small, irregular, pale, ashy-brown spots, not very perceptible, except on a rather close inspection. The gills consisted of three fleshy peduncles, which increased in size from the first to the last. They were beautifully branched from beneath, and along their lateral and terminal edges; and these little branches were divided and sub-divided into still more minute ramifications. This elegant fringe-work formed the true gills; the central and fleshy stalks serving merely as their support. Beneath, and rather in advance of these bodies, were three vertical clefts, through which the water was ejected backwards from the interior of the mouth upon the gills, though with a much more languid and less perceptible action than in fishes.

The general surface of this siren was very smooth, and no scales were apparent to the naked eye Towards the tail its form became thin and compressed, and that part was margined for several inches ---both above and below, as well as around its terminal point-by a narrow membrane or fin, which, no doubt, greatly aided its movements through the water.

* Menobranchus.

†M. pisciformis: Harlan.

+ Siren.

§ S. lacertina.

FISH is a name applied to all the species of a class of animals occupying the lowest station of the four great divisions of the section Vertebrata. A fish may, therefore, be defined a vertebrate animal, breathing through the medium of water, by means of branchiæ, or gills, having one auricle and one ventricle to the heart, cold red blood, and extremities formed for swimming.

The breathing apparatus is situated on each side of the neck, and consists of numerous luminæ, fixed on arches. These laminæ are covered with innumerable blood-vessels, and are so constructed as to present a considerable surface to the water, so that the blood may receive a sufficient portion of the oxygen contained in that element. As the water in contact with the gills becomes deteriorated, it is necessary that a constant current be caused to flow over them. In most fishes this is constantly effected by their taking the water in at the mouth and expelling it from under the gill-covers. The blood, which is sent to the branchine from the heart, is distributed by means of the arteries to every part of the body, whence it returns to the heart by means of the veins.

Every other part of the structure is equally well adapted to aquatic habits. The body is generally of an elongate, oval, compressed form, covered with scales directed backwards, and furnished with ins; thus being beautifully adapted for swimming. Many fishes, moreover, have a bladder filled with ir, situated immediately above the spine, by the dilatation or compression of which their specific gravity s said to be varied. The thoracic part of the body is thrown forwards towards the head, so that fishes may be said to have no neck, and thus the hinder part of the body is more free and fitted for motion. The limbs are formed into fins: the fore legs constituting what are termed the pectoral fins, and the osterior extremities the ventral. Besides these fins, ordinary fishes are furnished with one or two orsal fins, one anal fin, and a caudal fin, or tail.

The fins consist of a thin, elastic membrane, supported by rays. The rays are of two kinds: those which consist of a single bony piece, usually hard and pointed, are called spinous rays; and when the rays are formed of numerous portions of bone, united by articulations, and frequently divided longitudinally into several filaments, they are called flexible rays. The principal organ of motion is the tail; the dorsal and ventral fins apparently serve to balance the fish, and the pectorals to arrest its progress when required.

The scales are composed of two substances, one resembling horn in its texture, and the other of a harder and bone-like nature; they are generally attached to the skin by their anterior edge, and consist of numerous concentric laminæ, secreted by the skin, the smallest of which is first formed. Certain scales, forming a continuous series, in a slightly waved line from the head to the tail of a fish, are pierced in or near the centre, and furnished with a tube, through which a slimy matter is poured, which serves to lubricate the body of the animal. This series of tubes forms a line visible on the sides of the body, and which is termed the lateral line. These scales are pierced through near the centre by a little tube, that allows the exudation of the glutinous or mucous secretion, produced by glands beneath, and which thence spreads over the surface of the fish, defending it from the action of the

The gills of fishes are, in general, fringes on gill arches, as may be seen in the herring or salmon, protected by gill-covers. Each gill-cover, or operculum, is divided into five parts-the pre-operculum, the operculum, the sub-operculum, the inter-operculum, and the branchiostegous, or gill-covering rays In some fishes, as the eel, the branchial aperture is very small, and placed far behind the cavity containing the gills themselves. In the shark tribe the gills are fixed, there are no true gill-covers, the water escaping through fine branchial apertures on each side. In the flat skates, the mouth, nostrils, and branchial orifices are on the under surface, and the eyes on the upper surface, near which are two temporal orifices, which, while the fish reposes supine on the mud, admit the entrance of the water into the respiratory or branchial cavity, and also its exit. In the lamprey, seven orifices on each side of the neck lead to so many cells, performing the office of gills, and through these orifices the water is received and expelled. The teeth in fishes vary exceedingly; in some species they are disposed upon the jaws, the palate, the tongue, and the throat; in others, the mouth is destitute of teeth, while the throat or pharynx is provided with them. They differ also very greatly in form; in some fishes they are constructed for crushing; in others, for cutting; in others, for prehension; but in every instance their character accords with that of the food upon which the species habitually subsist.

The growth of fishes, more or less indefinite, is determined by food and temperature, and conse quently does not stop at a given point, and at a given date. And, as another peculiarity, they

reproduce their species long before attaining even their average size. Salmon, for example, hatched in the spring, return to the rivers for the purpose of breeding in the winter, or early in the next spring though only of the size to which the term "grilse" is applied. Trout, of the same age, in different rivers, vary from half a pound to six, seven, or eight pounds in weight, and, like the salmon, breed before they are half grown. The same remarks apply to other fish.

THE MUD-FISH.*

A VERY remarkable creature was to be seen at the Crystal Palace, Sydenham, a short time ago, which might be pronounced half fish and half reptile, and bore the name of the Lepidosiren, or Mud-fish. In 1837, several specimens of this animal were brought to this country from the river Gambia, in Western Africa, by T. C. B. Weir, Esq., one of which was presented to the Royal College of Surgeons in London; and an elaborate account of it, by Professor Owen, was published in the 18th volume of the "Linnæan Transactions."

The body of this creature is fish-like and elongated, the skin is covered with scales, a fin runs down the back and along the surface of the posterior part of the body. There are true gills and gillcovers; but the nostrils, unlike those of fishes, have an internal opening on each side of the mouth, between the lips and the outer edge of the large series of teeth; while their outer orifices are close together, on the under side of the inner lip.

Provided with true gills, the lepidosiren possesses also true air-breathing lungs, into which, as in the case of the frog or newt, the atmospheric air is forced by the action of the mouth, so that the animal respires both air and water. It has two anterior and two posterior elongated, awl-shaped appendages or limbs, which serve as supports to the body when resting at the bottom of the water, or when crawling on the mud; above the rest of the anterior limbs there are on each side two smaller appendages, which seem to aid in directing the movements of the creature in the water, through which it propels itself by the paddle-like action of the tail. Both the anterior and posterior limbs are fringed with a delicate membrane or web, and are exceedingly mobile and flexible, being used, as Dr. Gray observes, more like feet than fins, especially when they are within reach of some fixed body which the animal can use as a fulcrum. The sides of the head are furnished with lines of mucous pores, and there is a line of similar pores running down each side of the body, for about three parts of its length, becoming indistinct as they approach the tail. These pores plentifully exude a lubricating fluid, or mucous, with which the general surface of the animal is smeared. The specific title, annectans, given to it by Professor Owen, indicates its position in the scale of organic beings, forming, as it does, a link between reptiles and fishes, its structure exhibiting several of the leading characters of each of these classes.

In its native region, where it abounds, this creature dwells, during the hot and dry months, in the mud of the swamps along the Gambia, making for itself a convenient cavity, in which it remains, coiled up and dormant, till the return of the rainy season. Sometimes the case is almost or entirely composed of dry leaves, agglutinated together by the mucous secretion of the body. Mr. Daniel, who lived during several years on the Gambia and on Macarthy's Island, informed Dr. Gray that the lepidosiren is found only in the rice-fields, which are for more than half the year under water, and that they are procured by the natives towards the end of the dry season, when they are dug out of the nearly dried mud.

Miss Weir thus confirms this testimony in a note given in the paper already alluded to as found in the "Linnæan Transactions: "_"Fish taken in the summer of 1835, on the shores of Macarthy's Island, about three hundred and fifty miles up the river Gambia. They were found about eighteen inches below the surface of the ground, which, during nine months of the year, is perfectly dry and hard; the remaining three months it is under water. When dug out of the ground, and placed in water, the fish immediately unfold themselves, and commence swimming about. They are dug up with sharp stakes, and used as food." Another account states that they are eaten fried, and, like eels, have a rich, oily flavour.

VOL. IV.

* Lepidosiren annecians.

12

In June, 1856, Mr. Bartlett, the superintendent of the Natural History Department of the Crystal Palace, received from Western Africa four blocks of hard, dry, muddy clay, each one about the size of a quartern loaf, and sewn up carefully in a canvas wrapper. Captain Chamberlayne, who had sent them, directed that they should be placed in a tank of fresh water, at the temperature of eighty-three degrees. This was done, and in a short time the clay became softened, and crumbled away, and the inner case or cocoon, in which a lepidosiren was inclosed, floated motionless to the surface. This case, or cocoon, is probably nothing more than the layer of mud mixed with the mucous exuding from the body of the creature, so that it may have a proper degree of tenacity. The cavity is moulded by the coiled-up body, and often, perhaps usually, bears the impression of the scales.

It was not long before this cocoon became agitated: it was evident that the lepidosiren was endeavouring to extricate itself; a few struggles, and it had burst away; immediately it began to swim about, and then diving into the mud at the bottom of the tank, sheltered itself from further observation. The next morning two more lepidosirens emerged from their cocoons, and in the course of the following day the fourth of the party floated to the surface, but it was dead and putrescent.

The three living ones were meagre, and about nine inches long. Supplied with earthworms, small frogs, fish, and occasionally with raw flesh, they began very eagerly to feed. They did not, however, live together in peace, for they were seen at times assaulting each other. One of them, probably in an effort to escape from its antagonist, leaped out of the tank, and got into the large fountain-basin, where it remained among the gold-fish and the water-lilies. The two others lived on for some time, apparently agreed, when it was suddenly discovered that only one survived, having actually killed its companion, and, with the voracity of a cannibal, had left only the head and some part of the body, probably that which it liked least, undevoured. In three months it grew rapidly, actually doubling its length.

It was now transferred to the basin from which the other-the companion of the lilies and goldfish-was withdrawn, and placed again in the tank, but where it suddenly died; and thus the destroyer of his fellow alone survived. Here it continued to thrive at liberty, but was rarely seen, and when observed near the surface, it was apparently sick, and finally was taken out dead. The writer saw it repeatedly before this, and afterwards heard that it had now attained to twenty-eight and a-half inches in length, was no less than ten inches and a-half in circumference, and weighed four pounds and three quarters. A fine plaster cast was taken from this specimen by Mr. Bartlett, who also made a perforation of the skull, to show the remarkable structure of the teeth and jaws; while the skull, the viscera, and the muscular structure were preserved in spirits for after examination. The exterior of the animal has been carefully preserved, and may be seen by any visitor to the Reptile Department of the

British Museum.

Mr. Bartlett remarked, in a note to Dr. Gray :-"This creature masticates the food much, frequently putting it forward, almost quite out of its mouth, and then gradually chewing it back again. It rises frequently to the surface of the water to breathe, and at other times supports itself on its fin-like appendages, and, with the aid of its tail, raises its body from the ground, the fins being bent or curved backwards.

"The movement of this animal is generally very slow, and would give one an idea that it was very sluggish this, however, I have good reason to know is not the case, as, in attempting to capture the one at liberty in the large basin, it darted away with the rapidity of an arrow. I have reason also to believe that the animal finds its food as much by scent as sight. With reference to the cocoon, the end covering the nose of the animal is rather pointed, and has an aperture about the size of a pin's head, which I have no doubt enables it to breathe during its state of torpor. The animal, when in its case, is coiled nearly twice round; and I observed in each of the blocks of clay a small hole, about the size of a mouse-hole, which was quite smooth in the inside, as though the fish had crept through it."

An acquaintance with fishes-to which we now proceed-occupying the waters as thickly as animated beings do the land, and extending over three times their space, cannot but be desired by every lover of knowledge. But there are circumstances which render it of peculiar value to the people of our country; Great Britain possessing a coast-line of above 3,000 miles in extent, with a population more or less engaged in fisheries. Our shores are indented with bays and harbours, which protect the fisherman,