Page:Natural History, Fishes.djvu/287

Rh soft and leathery. The intestines are not furnished with cæca; but the air-bladder is generally well-developed.

About one hundred and fifty species are recognised as constituting this Family, some of which are exclusively marine, others exclusively fluviatile; while others, as our own common Eels, are found in both salt and fresh waters. They are widely scattered over most parts of the globe.

One of the most curious forms of the Family is that of the Gymnotus or Electric Eel, containing a few species peculiar to the rivers of tropical South America. The species best known, which has been exhibited alive in England, attains a length of five or six feet, with a diameter of eight inches. It has the power of communicating electric shocks of such violence, that the largest animals are stunned, and even destroyed by them. The organ which possesses this truly formidable power, consists of two large bundles of tendinous fibres on each side, occupying the hinder regions of the animal's body; these are crossed at right angles by other plates of the same kind, and thus a wide and deep network of cells is formed, each filled with a tremulous jelly; the whole organ may be likened to a powerful voltaic battery. Contact is not necessary for the exercise of its powers; it is said that shocks sufficient to kill other fishes are communicated through water to a distance of five or six yards.

The pectoral fins are well developed, though small, in this genus; the dorsal and anal are