Page:Natural History, Fishes.djvu/306

292 of maxillaries and intermaxillaries, are reduced, throughout the Order, to mere rudiments concealed beneath the skin: and the functions proper to them are performed by other bones of the mouth, as the palatals and the vomer.

Most persons who have ever looked at the backbone of any ordinary fish that is brought to table,—a Mackerel, a Cod, or a Salmon,—are aware that each vertebra is hollowed into a funnel-shaped cavity on each face, which is filled with a gelatinous substance: and that the centre is pierced with a slender hole, through which this jelly passes, thus forming a continuous cord, dilated and contracted alternately, throughout the spine. In many species of this Order the gelatinous cord varies very little in its diameter; and in some, the central tube of communication is so much enlarged as to reduce the solid part to a mere ring of cartilage.

It is observable that this Order presents us with some fishes having peculiarities of organization of a higher type than is found elsewhere in the whole Class, exhibiting a close affinity with the Reptiles; and even making a distinct approach to the Cetaceous. "The viviparous Sharks," says the learned author of Horæ Entomologicæ, "such as the Basking-Shark (Selache maxima, .), with their ear more perfectly organized than that of other fishes, and their body destitute of scales, the particular disposition of their fins, and their closed branchiæ, all indicate at what place we are to enter among the fishes upon leaving the Cetaceous quadrupeds."