Fishes that Carry Lanterns.
MANY curious forms of fishes have recently been found in the deep sea. One fish, dredged from a depth of nearly three miles, shows a complete modification of structure. At this distance from the surface the pressure can scarcely be realized. It is estimated that this fish has to contend against a pressure equal to two and a half tons to every square inch of surface. A sealed glass tube, inclosed in a perforated copper covering, has at two miles been reduced to fine powder, while the metal was twisted out of shape. Yet the fishes are so constructed that they can stand the pressure. Their bony and muscular systems are not fully developed; the bones are permeated with pores and fissures. The calcareous matter is at a minimum, and the bones of the vertebræ are joined together so loosely that in lifting the larger fishes out of the water they often fall apart. The muscles are all thin, and the connective tissue seems almost wanting. Yet these fishes are able to dart about and capture prey. Sunlight penetrates only about 1,200 feet below the surface of the sea; at 3,000 feet the temperature lowers to forty degrees Fahrenheit, and from about a mile from the surface to the bottom, four or five miles, the temperature is about the same the world over—just above freezing. How do the fishes and other forms that live there see? Their eyes are modified as well as their other parts. The fishes that live 500 feet from the surface have larger eyes than those in the zone above them, so that they can absorb the faint rays of light that reach them. In a zone below this many forms with small eyes begin to have curious tentacles, feelers, or organs of touch. Many of these deep-sea fish have special organs upon their sides and heads that are known to possess a luminous quality. Other organs are considered accessory eyes, so that the fishes have rows of eyes upon their ventral surfaces looking downward, while near are luminous spots that provide them with light. One of the largest of these deep-sea torch-bearers is a fish six feet long, with a tall dorsal fin extending nearly the entire length of the body. The tips of this fin are luminous, and also a broad patch upon its head. Along the sides of the body is a double row of luminous spots. One of the most ferocious of these deep-sea monsters is the chauliodus. Its mouth is fairly overflowing with teeth that protrude in a most forbidding manner. The fins are all tipped with flaming spots, while along the dorsal surface extends a row of spots that appear like so many shining windows in the fish, through which light is shining. The little fishes called Bombay ducks are luminous over their entire surface, and when numbers are collected together they present an astonishing spectacle. One of the most interesting of these light-givers is the chiasmodus, a fish that attains the length of only thirteen inches. The top of its head is the principal light-giving organ, and the fins gleam with phosphorescent light. It is not alone remarkable as a light-giver; it has a jaw so arranged that it can seize fish twice its size and swallow them. Its stomach has the elastic quality of India rubber. It stretches to enormous proportions, and appears like a great transparent balloon hanging under the fish and containing its prey. The last expedition sent out by France brought to light some remarkable forms. The dredge off Morocco brought up from a depth of one and a half miles a fish that appeared to be all head or mouth. It was of small size, and the length of the mouth was about four-fifths of the entire body; so that, if the body had been severed behind the head, it and two or three like it could have been stowed away in its capacious pouch. It probably moves very slowly, scooping mud and ooze into its mouth, sifting out the animal parts and rejecting the rest.—Philadelphia Record.