But do the Placoids possess in reality a large development of brain? I have examined the brains of almost all the common fish of our coast, both osseous and cartilaginous, not, I fear, with the skill of a Tiedemann, but all the more intelligently in consequence of what Tiedemann had previously done and written: and so I can speak with some little confidence on the subject, so far at least as my modicum of experience, thus acquired, extends. Of all the common fish of the Scottish seas, the spotted or lesser dog-fish bears, in proportion to its size, the largest brain; the gray or picked dog-fish ranks next in its degree of development; the Rays, in their various species, follow after; and the osseous fishes compose at least the great body of the rear; while still further behind, there lags a hapless class—the _Suctorii_, one of which, the glutinous hag, has scarce any brain, and one, the _Amphioxus_ or lancelet, wants brain altogether. I have compared the brain of the spotted dog-fish with that of a young alligator, and have found that in scarce any perceptible degree was it inferior, in point of bulk, and very slightly indeed in point of organization, to the brain of the reptile. And the instincts of this Placoid family,—one of the truest existing representatives of the Placoids of the Silurian System[25] to which we can appeal,—correspond, we invariably find, with their superior cerebral development. I have seen the common dog-fish, _Spinax Acanthias_, hovering in packs in the Moray Frith, some one or two fathoms away from the side of the herring boat from which, when the fishermen were engaged in hauling their nets, I have watched them, and have admired the caution which, with all their ferocity of disposition, they rarely failed to manifest;—how they kept aloof from the net, even more warily than the cetacea themselves,—though both dog-fish and cetacea are occasionally entangled;—and how, when a few herrings were shaken loose from the meshes they at once darted upon them, exhibiting for a moment, through the green depths, the pale gleam of their abdomens, as they turned upon their sides to seize the desired morsels,—a motion rendered necessary by the position of the mouth in this family; and how next, their object accomplished, they fell back into their old position, and waited on as before. And I have been assured by intelligent fishermen, that at the deep-sea white-fishing, in which baited hooks, not nets, are employed, the degree of shrewd caution exercised by these creatures seems more extraordinary still. The hatred which the fisher bears to them arises not more from the actual amount of mischief which they do him, than from the circumstance that in most cases they persist in doing it with complete impunity to themselves. I have seen, said an observant Cromarty fisherman to the writer of these chapters, a pack of dog-fish watching beside our boat, as we were hauling our lines, and severing the hooked fish,