Blumenbach, in his Manual of Natural History, thus mentions the reproductive power and independent vitality with reference to the Amphibia:—“The extraordinary strength of the reproductive power in several Amphibia, and the astonishing facility with which the process is carried on, depend, if I mistake not, on the great magnitude of their nerves and the diminutive proportion of their brain. The former parts are, in consequence, less dependent on the latter; hence the whole machine has less powers of motion, and displays less sympathy; the mode of existence is more simple, and approaches more nearly to that of the vegetable world than in the warm-blooded classes; but, on the contrary, the parts possess a greater individual independent vitality. Since, in consequence of this latter endowment, stimuli which operate on one part, or one system, do not immediately affect the whole frame by sympathy, as in warm-blooded animals, we are enabled to explain the peculiar tenacity of life which is displayed under various circumstances in this class—viz. frogs still continue to jump about after their heart has been torn out, and turtles have lived for months after the removal of the whole brain from the cranium. The long-continued power of motion in parts which have been cut off from the body, as in the tail of the water-newt and blind-worm, may be explained upon the same principles.” The length of time that this irritability exists in snakes, has given rise to the opinion of the vulgar, that “if a snake is killed in the morning, it will not die before sunset.” Among numerous instances of irritability in the warm-blooded class, shortly after death the heart may be stimulated to perform its natural action, by being punctured; and in a limb after amputation, the muscles are excited to contract by a scalpel being plunged into them. The sucking-fish is commonly found adhering to the body of the shark. It is placed, by Cuvier, among the third order of fishes, or the _Malacoptérygiens subbrachiens_, which is characterized “Par des ventrales attachées sous les pectorales, et dont le bassin est immédiatement suspendu aux os de l’épaule.” Its generic character is as follows:—Head furnished above with a flat, ovate, transversely sulcated shield. Gill membrane six-rayed. Body without scales. When first removed from the water, the colour of the fish of the common species was an uniform grey or lavender, which soon changed to a brownish colour; the tail was forked, or rather crescent-shaped. The sucking-plate, of an oval form, was situated on the upper part of the head, and was composed of seventeen transverse moveable cartilaginous plates, (but they vary in number, according to the size of the fish,) each armed with minute teeth directed backwards; from which cause it was difficult to detach the animal in a direction perpendicular or backwards, but it was removed with facility when drawn off in the direction of the head.