When we penetrate beyond a certain depth, we find blind fishes as well as those possessing eyes; and all the forms of the greater depths are adapted to their life under the consequent enormous pressure in a remarkable manner. The bones are friable and cavernous, and loosely connected. Many are covered with a thick mucus, while many more have curious plates, that are so many torches or lanterns to emit light for their possessors. As some of the fishes have eyes and no phosphorescent organs, while others are luminous and perhaps blind, and knowing that all are carnivorous, we may well imagine that a fierce struggle for existence is carried on in this distant world of the sea. The lamps of some forms must attract their enemies; while, on the other hand, they may constitute a lure, dazzling weaker forms, which fall victims to their curiosity. Among all the light-givers, these deep-sea lantern-bearers are the most interesting, and typical of the mysterious realm from which they are taken by the ingenious inventions of mankind. Some are luminous over their entire surface, as the _Harpodon_, or Bombay duck (Plate XVIII., Fig. 2). Others have a series of plates extending along the side, that resemble the open ports of a steamer. Some possess gleaming head-lights, the locomotives of the sea; while others have their lights confined in groups. While the expeditions of the “Challenger,” “Talisman,” “Albatross,” and “Travailleur” have resulted in the discovery of what seems a remarkable presentation of these light-givers, we can well imagine, understanding the difficulties of deep-sea dredging, that the largest and perhaps most interesting of these forms are yet undiscovered, and that the greatest mysteries may never be revealed. The difficulties that attend, and the chances against, the capture of deep-sea fishes, can be perhaps realized by my young readers, if they imagine a large balloon sailing along over the country at an elevation of from four to five miles, dragging a dredge ten or twelve feet wide. Few active boys or girls would be caught by such a device; only the sluggards that were fast asleep would be trapped. The comparatively small dredge at the end of a six-mile rope, dragging along and creating an unusual commotion in the silent submarine world, secures only a few forms, the sluggards and mud-lovers, as a rule: so that fishes taken at extreme depths are prizes indeed. The “Talisman” took the fish _Bythites crassus_ from a depth of about two miles. The naturalists of the “Challenger” expedition captured the _Bathyophis ferox_ about three miles from the surface, or, to be exact, five thousand and nineteen meters. The American exploring-vessel, the “Albatross,” under the direction of Professor Spencer F. Baird, has exceeded any of these hauls; in 1883 making a capture of five species in twenty-nine hundred and forty-nine fathoms.