DISCOBOLI ;- -SUCKING-FISH.-MURÆNIDE.

51

From this

species of fish would be swept away by the current. curious conformation, they have received the name of DISCOBOLI. Their skin is slimy and naked, or with hard grains imbedded in it. Their pectoral fins are large; and they swim with great vivacity in shallow water, and near coasts. Several species of this family, most of them small, are found on the south and west coasts of England. One of the largest is known as the Lumpfish; this is found as far northwards as the margin of the Polar ice, and is a palatable article of food; its name is derived from the clumsiness of its form, its height being about half its length, and its thickness about half its height. The Remora, or Sucking-fish, (§ 529), is placed by Cuvier in this family, although its disc, or sucker, is so entirely different in its position; but he remarks, that it might be placed by itself, as the type of a distinct family.

ORDER IV.-MALACOPTERYGII APODA.

576. The fishes in which the ventral fins are always wanting, form but a single natural family; MURENIDE, or the Eel tribe. These are at once known by their long, slender, snake-like bodies, covered with a soft skin, and having the scales very minute, and often almost invisible. The gill-orifices are very small, and are prolonged far back, so that a sort of long passage is formed from the branchial chamber to the surface of the body. In this manner the gills are so much sheltered, that the fish can remain out of the water for a considerable time, without those organs being rendered unfit (by becoming dry), to carry on the respiration. Of course, the access of water to the gills cannot at any time be so free, as it is in fishes with large gill-openings; and their respiration may be habitually less. It is in animals with a feeble respiration, as has been already remarked in the case of Reptiles, that we find the greatest tenacity of life; and every one knows the difficulty with which the Eel is killed-the most cruel injuries being sustained by it without the loss of its vitality. The ordinary Eels, of which there are several species,

52

MURÆNIDE, OR EEL-TRIBE.

inhabit ponds, rivers, and the brackish water at the mouths of rivers. In the autumn they make their way to the sea in vast numbers; for the purpose, it is believed, of depositing their spawn. Myriads of minute Eels, three or four inches long, are seen in the spring, making their way up rivers, and dispersing into the tributary streams as they proceed; but whether the parent Eels thus return is uncertain. It is well known that the Eels which inhabit inland lakes and ponds, whence they cannot escape to the sea, are able to breed without this migration; but it appears that their season is somewhat later, the water in such situations being colder than that of the sea in the early spring. Eels frequently quit the water, in warm, damp nights, and wander over the grass; either in quest of worms, frogs, or other food; or in order to change their locality.-Many of this family are chiefly marine; though they occasionally stray into the mouths of rivers: this is the case, for instance, with the Conger, which is one of the largest of the whole order, sometimes measuring six feet in length, and being as thick as a man's leg.— The Ophisurus, or Snake Eel (so called from its strong resemblance to a serpent) of the Mediterranean, attains the same length, but is not so thick. In the genus Murana, and its allies, the pectoral as well as the ventral fins are wanting; and the gillopenings are extremely small. This, too, is a Mediterranean fish ; it was much esteemed by the ancients, who kept it carefully in ponds; and there is a well-known story of a cruel master, who caused his offending slaves to be flung alive into the ponds, to feed the Murænæ. The common species grows to the length of three feet or more; its surface is mottled brown and yellow; and it is very voracious and ugly. In some of the genera nearly allied to this, the gill-passages unite, so as to open externally by a single orifice on the under side of the neck; and in several of these, we find the air-bladder almost as completely presenting the characters of a rudimentary lung, as in the Sauroid Fishes (§ 588).

577. The Gymnoti, or Electric Eels (§ 540), and their allies, have been separated from the preceding family by some naturalists, on account of the less complete inclosure of the gill-covers

EEL-TRIBE.-LOPHOBRANCHII.

53

by the skin, and of the absence of the dorsal fin (Fig. 262). It is to the true Gymnotus, that the electric power is confined; and the group includes several other genera, of which some belong to the British seas. Of these may be mentioned the Leptocephalus, or Morris, which is a small riband-shaped fish, with a body so thin and transparent that its internal structure can be seen without dissection; it lurks among sea-weeds, and is very lively in its motions. The Amnodytes, or Launces,-one of which is known to fishermen by the name of the Sand-Eel, and another as the Sand-Launce,-are remarkable for their habit of burrowing in the sand, in which they find the worms that constitute their chief food. They become in their turn the prey of the Salmon; to whose support, whilst they are in the estuaries of rivers, the Launces are believed to contribute largely.

ORDER V.-LOPHOBRANCHII.

578. This order consists of a small group, which is separated from all other Osseous Fishes by the structure of the gills; which, instead of hanging from the branchial arches in fringes of parallel fibres, disposed like the teeth of a comb, are set upon them in small round tufts, arranged in pairs. From this peculiar conformation, the name of the order, which signifies tuft-gilled, is derived. The gills are defended by a large operculum, which is attached by a membranous covering on all sides, except at one part where a small hole is left for the escape of the water. These fishes are also distinguished by having their body covered with shields or small plates, which often give it an angular form. In general they are of small size, and often without flesh. They do not present many points of general interest; but there are certain peculiarities in their organisation, which are very interesting to the Naturalist. In the Syngnathus, or Pipe-fish, which has a prolonged muzzle like that of the Fistularidæ (§ 566), the eggs are not deposited as in other Fishes, but are conveyed. into a sort of pouch, formed by a doubling of the skin under the body of the male; this pouch is under the abdomen in some

54

PIPE-FISH; HIPPOCAMPUS. PLECTOGNATHI.

species, and at the base of the tail in others. In this pouch the eggs become matured; and when the fry are ready to escape, it opens and allows them to pass out. This contrivance reminds us of the pouch of the Marsupial Mammalia; but there is this striking difference, that in the latter it is the Female which affords this protection to the young, whilst in the Pipe-fishes it is the Male. It has been asserted that, even after the young have quitted the pouch, they will return to it again; and that the parent shows great attachment to them. The Hippocampus (Fig. 259) has a prehensile tail, unfurnished with any finny expansion; and is enabled by its means to climb or hold on by the stalks of marine plants. It is only in the dead specimen, that the neck acquires the peculiar bend, which gives its head the resemblance to that of a Horse, from which its name is derived. The Pegasus, though furnished with a snout, has the mouth beneath it; the pectoral fins are large, and are spread out in a wing-like manner; whence these curious Fishes have derived their name, which signifies Flying Horses.

ORDER VI.-PLECTOGNATHI.

579. We next come to another small order, which forms a connecting link between the Osseous and Cartilaginous fishes. It resembles the latter, in having the upper jaw attached to the cranium, in such a manner as to possess but little power of motion (whence is derived the name of the Order, which means having the jaws soldered), and also in the imperfect ossification of the skeleton. Still, in its general conformation, the skeleton rather resembles that of the bony fishes. The gill-lid is concealed under the thick skin, as in the preceding Orders; and there is but a small gill-opening on either side: the ribs are scarcely developed. This Order includes two families, which are distinguished by the structure of their teeth. In the first of these, the Gymnodontes, or Fishes with naked teeth, the jaws are shaped like the beak of a Parrot; and are composed of parallel plates of a substance resembling ivory. These are reproduced as

GLOBE-FISH; SUN-FISH.—BALISTIDÆ.

55

fast as they are destroyed by wear; and they constitute very efficient instruments for grinding down the food on which these animals live, which consists of Crustacea and sea-weeds. To this family belong the Globe-fishes; which are so named from their power of distending themselves into a spherical form, by inflating with air a large sac contained in the abdomen. When thus distended, they float along the water with the back downwards, swimming onwards by means of their pectoral fins; and they are covered with a series of large spines, which are raised up when the body is thus inflated, so as to form a very efficient means of defence. From this last circumstance, these Fishes have been sometimes termed Porcupine-fish. There are three genera in which this curious power exists; the Diodon (two-toothed), in which there is no furrow or division in the jaws, so that each seems like a single tooth ;-the Triodon (three-toothed), in which there is a division in the centre of the upper jaw; so as to divide it, as it were, into two teeth;-and the Tetrodon (fourtoothed), in which there is a division of this kind in each jaw. Besides these, this family contains the Orthagoriscus, or Sun-fish (so named from its rounded form), which looks like the anterior half of a fish cut in two in the middle. It has the power of floating with its head and eyes above water; but not of distending itself with air; in this state it moves along sideways, very slowly, however; and appears like a dead or dying fish. The Sun-fish (or Moon-fish, as it is sometimes called) attains a considerable size; of the short species, which is most remarkable for its peculiarity of form, individuals have been frequently caught measuring four feet in length, and nearly as much in breadth, and weighing 400 lbs. ; and it has been stated occasionally to attain double that weight.

580. In the second family, that of BALISTIDE, or File-fishes, the jaws are armed with a small number of distinct teeth; the skin is either rough, or covered with very hard scales,-whence their name, and the mouth is prolonged into a sort of pyramid. In their general form, and in the brilliancy of their colours, they bear a considerable resemblance to the Chaetodons (§ 556); and, like them, they inhabit the seas of warm regions, keeping near