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.
On inspecting the mouth I observed two rows of teeth situated on the margin of each jaw, one internal to the other, the outer row being larger and stronger than the inner; and it is probable that the inner row is intended, as in the shark, to replace the front row, when lost from time or accident. On the palate were also placed two rows of very fine teeth, and the other parts of the mouth were rough. I made several dried preparations of the head of this fish, which well displayed the form of the disk; and, by keeping the mouth distended, the rows of teeth could be distinctly seen and examined.
The fins are, two pectoral, two ventral, one dorsal, and one anal; the whole of which are of small size, in proportion to the body of the fish, as well as the tail. The disproportion of the size of the head, and the diminutive size of the fins and tail, must consequently prevent its swimming to any distance, for when swimming its motion is very tardy, and apparently laborious. Nature has, therefore, provided it with a means of attaching itself to rocks, the bottoms of ships, &c.
I have seen them attached more commonly to the body of the Squalus carcharias, or white shark, than to any other species: whether it is that this species of shark is the most usually met with, I cannot determine; but on a blue shark, although accompanied by pilot-fish, I never, in the few instances I have met with, saw a Remora attached, although, in the other species, I have always seen some attached: if this, on further observation, is found to be the fact, it may be probably accounted for by the Squalus carcharias more frequently approaching the land. The sucking-fish not being able to swim any distance, must generally remain attached to rocks, &c., and from them removes itself to the shark as he approaches.
The sucking-plate enables these fish to change their locality, by attaching themselves to the stronger inhabitants of the deep, and precludes, as on the rocks, the danger of their being driven by tempests remote from their usual food and rest. This fish is also destitute of an air-bladder.
The Remora was supposed, by the ancients, to have the power of arresting the progress of a ship under full sail; and, by others, their nourishment was supposed to be derived from the body of the shark, or from any substance to which it adhered: all these chimeras have, however, been long since dispersed. Their food has been found (from the examination of the contents of the stomachs of the specimens captured) to be minute marine insects, &c.
I have seen the Remora of a very large size. During a visit to the island of Tongatabu, one of the Friendly group, on August 1st, 1829, several were brought on board for sale, by the natives, which measured three feet and upwards in length. They had taken them with a hook and line. They were cooked, and found delicate and well-tasted. During also our passage through the straits of St. Bernardin to Manilla, several, of a large size, were seen swimming about the ship, but their movements were slow and heavy.