The “Electric Eel” is the most powerful of electric fishes, growing to a length of six feet, and extremely abundant in certain localities of Brazil and the Guyanas. The electric organ consists of two pairs of longitudinal bodies, situated immediately below the skin, above the muscles; one pair on the back of the tail, and the other pair along the anal fin. Each fasciculus is composed of flat partitions or septa, with transverse divisions between them. The outer edge of the septa appear in nearly parallel lines in the direction of the longitudinal axis of the body, and consist of thin membranes, which are easily torn; they serve the same purpose as the columns in the analogous organ of the Torpedo, making the walls or abutments for the perpendicular and transverse dissepiments, which are exceedingly numerous, and so closely aggregated as to seem almost in contact. The minute prismatic cells, intercepted between these two sorts of plates, contain a gelatinous matter; the septa are about one-thirtieth of an inch from each other, and one inch in length contains a series of 240 cells, giving an enormous surface to the electric organs. The whole apparatus is supplied with more than 200 nerves, which are the continuations of the rami anteriores of the spinal nerves. In their course they give out branches to the muscles of the back, and to the skin of the animal. In the Gymnotus, as in the Torpedo, the nerves supplying the electric organs are much larger than those bestowed on any part for the purposes of sensation or movement.
The graphic description by Humboldt of the capture of Electric Eels by horses driven into the water, which would receive the electric discharges and thus exhaust the fishes, seems to rest either on the imagination of some person who told it to the great traveller or on some isolated incident. Recent travellers have not been able to verify it even in the same parts of the country where the practice was said to exist.
Thirtieth Family—Symbranchidæ.
Body elongate, naked or covered with minute scales; barbels none. Margin of the upper jaw formed by the intermaxillaries only, the well developed maxillaries lying behind and parallel to them. Paired fins none. Vertical fins rudimentary, reduced to more or less distinct cutaneous folds. Vent situated at a, great distance behind the head. Ribs present. Gill-openings confluent into one slit situated on the ventral surface. Air-bladder none. Stomach without cæcal sac or pyloric appendages. Ovaries with oviducts.
The fishes of this family consist of freshwater-fishes from tropical America and Asia, which, however, enter also brackish water; and of a truly marine genus from Australia.
Amphipnous.—Vent in the posterior half of the body, which is covered with minute scales longitudinally arranged.
A common fish (A. cuchia) in Bengal, remarkable for its singular respiratory apparatus. It has only three branchial arches, with rudimentary branchial laminæ, and with very narrow slits between the arches. To supplement this insufficient respiratory apparatus, a lung-like sac is developed on each side of the body behind the head, opening between the hyoid and first branchial arch. The interior of the sac is abundantly provided with blood-vessels, the arterial coming from the branchial arteries, whilst those issuing from it unite to form the aorta. A. cuchia approaches the Eels in having the humeral arch not attached to the skull.
Monopterus.—Vent in the posterior half of the body, which is naked. Three branchial arches with rudimentary gills, but without breathing sac.
One species (M. javanicus), which is extremely common in the East Indian Archipelago and in the eastern parts of the Continent. Upwards of three feet long.
Symbranchus.—Vent in the posterior half of the body, which is naked. Four branchial arches with well developed gills.