Its tail is long, flexible, and slender, acting at once as a rudder and a weapon of offence or defence. When lying in ambush, nearly buried in mud at the bottom of the sea, and it has no desire to change its position, a rapid and sudden stroke of this formidable weapon, armed with hooked bones on its upper surface, arrests its victim by wounding or killing it, without disturbing the mud or seaweed by which it is covered. This species sometimes attains a very considerable size, and their flesh is firm and nourishing; but the larger specimens rarely approach inhabited shores, even when the female desires to lay her eggs. These eggs have a very singular shape, differing from almost every other fish, and particularly from those of all other osseous fishes. They are quadrangular, a little flat, each of the four corners terminating in a small cylindrical beak—a kind of pocket formed of a strong and transparent membrane.
The Lump-fish, R. clavata (Fig. 350), so called in consequence of its armature, inhabits every European sea; sometimes it attains the length of twelve feet, and, being excellent eating, is much sought after by fishermen. It is frequently seen with the skate in European markets. A ray of great curving spines occupies the back and extends to the end of the tail; two similar spines are above, and two below the point of the muzzle. Two others are placed before, and three behind the eyes. Each side of the tail is furnished with a row of shorter spines; the whole surface, in short, bristles with larger or smaller spines, justifying the name of buckler-fish; for these are not given by way of ornament, but defence. The colour of the upper surface is generally brown, with whitish spots. The tail, which exceeds the body in length, presents towards the end two small dorsals, terminating in a caudal fin.
Fig. 351. The Cramp-fish (Torpedo marmorata).
Ray-fish of all kinds are inhabitants of the deep sea, but they change according to the seasons. While stormy weather prevails, they hide themselves in the depth of the ocean, where they lie in ambush, creeping along the bottom. But they do not always live at the bottom. They rise occasionally to the surface far from the shore, eagerly chasing other inhabitants of the deep, lashing the water with their formidable tails and fins, springing out of the water, and making it foam again under their gambols.
When pursuing their prey the rays employ their great pectoral fins, which resemble wings, and are aided by a very delicate and mobile tail; they beat the waters in order to fall unexpectedly upon their prey, as the eagle swoops down upon its victim. It may thus be called the king of fishes, as the eagle is the king of birds.
The Cramp-fish, Torpedo marmorata (Fig. 351), has considerable analogy with the Raia. Its flattened body forms a roundish disk, beyond which its rays form large pectoral fins; but the humeral girdle which carries them, carries also, in a great hollow, a most singular organic apparatus, which possesses the property of producing violent electrical commotions. This apparatus is placed in the interval between the end of the muzzle and the extremity of the fin, and completes the rounded disk of the body. The mouth is small, the slit crosswise; the jaws bare; the teeth in squares of five. The eyes are small; behind them are two star-like spout-holes. On the lower surface of the breast are two rows of small transverse slits, openings of the gill pouches, like those of the rays. The tail is thick, short, and conical, carrying part of the ventral, and terminating in a sort of caudal fin. On the back are two small, soft, and adipose fins. The skin is smooth; its colour varies with the species; generally it is reddish-brown, with eye-like spots of a deep blue in the centre; sometimes azure, and surrounded by a great brownish circle; the spots being five or six. These curious fishes are found in the Channel and on the shores of the Mediterranean.
The electrical effects produced on the fisherman who seizes them were noted from early times; but Redi, the Italian naturalist of the seventeenth century, was the first who studied them scientifically. Having caught and landed one of them with every precaution, "I had scarcely touched and pressed it with my hand," says the Italian naturalist, "than I experienced a tingling sensation, which extended to my arms and shoulders, which was followed by a disagreeable trembling, with a painful and acute sensation in the elbow joint, which made me withdraw my arm immediately."
Réaumur also made some observations upon the Torpedo. "The benumbing influence," he says, "is very different from any similar sensation. All over the arm there is a commotion which it is impossible to describe, but which, so far as comparison can be made, resembles the sensation produced by striking the tender part of the elbow against a hard substance." Redi remarks, besides, that the pain and trembling sensation resulting from the touch diminishes as the death of the Torpedo approaches, and that it ceases altogether when the animal dies.