The rays have broad flattened bodies, and very long and slender tails. In consequence of this structure they cannot swim by means of their tails, as nearly all other fishes do, but travel slowly through the water by waving their side fins, after the manner of soles and flounders. One of the best known of these fishes is the skate, which when fully grown sometimes measures as much as six feet in length from the snout to the tip of the tail, and five feet in width of body. As it cannot swim fast enough to overtake other fishes, it preys chiefly upon crabs, lobsters, and shell-bearing mollusks, which it finds on the bottom and is able easily to crunch up, shells and all. The eggs of this fish may be found in great numbers on the sea-shore. They are very much like those of the dogfish, but are nearly black in color, and instead of a long twisted tendril at each corner, they only have a blunt projection about an inch long. They remind one, in fact, of a hand-barrow, and consequently the fishermen often call them "skate-barrows." In color, the skate is grayish brown above and grayish white beneath. Another very curious ray is the torpedo, which is an electric fish, having a kind of electric battery inside its body, from which a very powerful shock can be discharged at will. This battery, in appearance, is something like a honeycomb, consisting of a number of six-sided columns, which run from the skin of the back to that of the lower surface of the body. Each of these columns is divided into a number of cells, or chambers, by thin walls of membrane; and each cell contains a liquid which seems to consist chiefly of salt and water. The electricity produced and stored up in these organs seems to be discharged along four great nerves, which run from the battery up to the brain. The shock is sufficiently strong to kill a duck; and not only has an electric bell been rung by it, but an electric spark has been actually obtained. And when five persons held one another's hands, and the person at each end laid his finger upon the torpedo, every one of the five persons felt the shock. Even more formidable, though in quite a different way, is the sting-ray. At the base of its long whip-like tail this fish has a bony spine set with sharp teeth, like a saw; and its favorite mode of attack is to coil this tail round the body of its victim and then to drive the spine into his flesh, working it backward and forward in such a manner as to cause a very serious wound always followed by severe inflammation. Some of the rays in the warmer seas grow to a very great size; indeed, a ray measuring over eighteen feet in length has more than once been captured. They are dangerous creatures to meddle with, for a fish of this size is quite strong enough to overturn a boat, while if a man were once seized by one of them, he would have very little chance of escape. These huge creatures are generally known as devil-fish. THE STURGEON