Page:Natural History, Fishes.djvu/26

12 Roach have only a few strong teeth in the throat, and a single flat one above; and the Sturgeon, the Pipe-fish, and the Sandlance, are entirely toothless.

The blood, as already observed, commonly takes the temperature of the surrounding element; in some of the swift oceanic Fishes of the Mackerel family, however, such as the Tunny and the Bonito, the blood is found to be 10° higher than the temperature of the surface of the sea, even within the tropics: the flesh of these Fishes is dark and dense. The blood-disks are sometimes circular, sometimes oval; they are larger than those of Mammalia and Birds; smaller than those of Reptiles, and especially than those of Amphibia.

The brain is small, and is divided into a succession of lobes or ganglionic masses, "most of them exclusively appropriated to the function of a nerve of special sense." The senses are possessed probably in very different degrees. Touch is considered to be feebly exercised; but the thick and fleshy lips of the Wrasses, the whiplike filaments of the Anglers, the beards of the Cod and Barbel, and the long flexible fingers in the pectoral fins of the Gurnards may be the seats of special sensations of feeling. Taste is even still more dubious. The bony character of the mouth, and the manner in which the tongue is often covered with teeth, combine with the circumstance that the food is almost invariably swallowed whole the instant it is seized,—to forbid the supposition of acute taste.

The sense of smell is probably possessed in considerable perfection by Fishes. The olfactory