The third order, _Selachia_, includes a number of cartilaginous fish, varying much in form; the rays, dog‐fish, skate, torpedo, shark, and saw‐ fish belong to this important division. The torpedo has the power of giving a strong electrical shock. Redi, an Italian naturalist of the seventeenth century, first studied them carefully. He caught and landed an electric ray, and pressing it with his hand, experienced a tingling sensation, which extended to his arms and shoulders, and was followed by a disagreeable trembling. This electric power dies with the animal. Dr. Walsh made some interesting experiments with them. He placed a living torpedo on a clean wet towel, and connected brass wires with it. Round the torpedo were eight persons, standing on isolating substances. One end of the wire was placed in a basin full of water. The first person had a finger of one hand in this basin, and a finger of the other in a second basin, also full of water. The second person had a finger in the last‐ named basin, and a finger of the other hand in a third basin, and so on round the circle of eight persons. The end of the second wire was plunged into the last basin of the series, thus establishing a complete electric circuit. At the moment when the experimenter touched the torpedo a tolerably strong shock was felt by all participating. When the torpedo was placed on an isolated supporter, it showed its energy by communicating to several persons forty or fifty shocks in the short space of a minute and a half. The family _Carcharidæ_ includes the true sharks, some species of which attain to a length of twenty, or even thirty, feet. They are the terror of all other fish and molluscs. “But the prey which has the greatest charm for him is man; the shark loves him dearly, but it is with the affection of the gourmand. If we may believe some travellers, when several varieties of human food comes in its way, the shark prefers the European to the Asiatic, and both to the negro.” He has been known to jump clean aboard a fisherman’s boat, and even to snap up a sailor from the shrouds. Commerson relates the following:—The corpse of a negro had been suspended from a yard‐arm _twenty feet_ above the level of the sea. A shark was seen making every effort to reach the body, which eventually he did, and tore it limb from limb in presence of the horror‐stricken crew. The mouth of the shark is placed in the lower part of the head, and the animal has to turn itself in the water before he can seize an object above him. On the African coast the negroes take advantage of this fact; they swim towards him, and seize the moment when he turns to rip up his belly with a large strong knife. The adult shark has six rows of murderous‐looking teeth, forming a perfect arsenal of deadly weapons.