Electric fishes

ALL ANIMALS in the phylogenetic scale above those which have tissues but no organs, which is to say that all animals above and including the most primitive worms, have developed some sort of mechanism that both produces and operates on electricity. In almost all animals this is a purely internal phenomenon, the nervous system, by means of which the creature sees, hears, feels, tastes, smells, moves, and thinks — if it thinks at all. In a few very special animals, there has been developed a modification of this in that some of the electricity produced can be released outside the body rather than being confined within it. All of these animals are fishes, which is not surprising, for it would not do a terrestrial animal, a bird or insect, for instance, much good to have electricity which can be released outside the body when there is no medium to conduct it. Why only some fishes have produced this peculiar mechanism, or why any of them did so, is something about which we can only conjecture, but it remains that a number of fishes, some extinct and some living at present, have developed it.