=Electric Fishes.=--Several species of fishes possess the power to inflict electric shocks not unlike those of the Leyden jar. This is useful in stunning their prey and especially in confounding their enemies. In most cases these electric organs are evidently developed from muscular substance. Their action, which is largely voluntary, is in its nature like muscular action. The power is soon exhausted and must be restored by rest and food. The effects of artificial stimulation and of poisons are parallel with the effect of similar agents on muscles. [Illustration: FIG. 140.--Electric Catfish, _Torpedo electricus_ (Gmelin). Congo River. (Alter Boulenger.)] In the electric rays or torpedos (_Narcobatidæ_) the electric organs are large honeycomb-like structures, "vertical hexagonal prisms," upwards of 400 of them, at the base of the pectoral fins. Each prism is filled "with a clear trembling jelly-like substance." These fishes give a shock which is communicable through a metallic conductor, as an iron spear or the handle of a knife. It produces a peculiar and disagreeable sensation not at all dangerous. It is said that this living battery shows all the known qualities of magnetism, rendering the needle magnetic, decomposing chemical compounds, etc. In the Nile is an electric catfish (_Torpedo electricus_) having similar powers. Its electric organ extends over the whole body, being thickest below. It consists of rhomboidal cells of a firm gelatinous substance. The electric eel (_Electrophorus electricus_), the most powerful of electric fishes, is not an eel, but allied rather to the sucker or carp. It is, however, eel-like in form and lives in rivers of Brazil and Guiana. The electric organs are in two pairs, one on the back of the tail, the other on the anal fin. These are made up of an enormous number of minute cells. In the electric eel, as in the other electric fishes, the nerves supplying these organs are much larger than those passing from the spinal cord for any other purpose. In all these cases closely related species show a no trace of the electric powers. [Illustration: FIG. 141.--Star-gazer (_Astroscopus guttatus_) settling in the sand. (From life by R. W. Shufeldt.)] Dr. Gilbert has described the electric powers of species of star-gazer (_Astroscopus y-græcum_ and _A. zephyreus_), the electric cells lying under the naked skin of the top of the head. Electric power is ascribed to a species of cusk (_Urophycis regius_), but this perhaps needs verification.