The different depths affect the inhabitants to a more or less extent. In some, the eyes seem to have lost their proper functions; and an instance is thus described by the Rev. A. M. Norman, naturalist of the “Porcupine,” the crustacean being _Ethusa granulata_: “The examples at one hundred and ten to three hundred and seventy fathoms in the more southern habitat have the carapace furnished in front with a spinose rostrum of considerable length. The animal is apparently blind, but has two remarkable spiny eye-stalks, with a smooth rounded termination where the eye itself is ordinarily situated. In the specimens, however, from the north, which live in five hundred and forty-two and seven hundred and five fathoms, the eye-stalks are no longer movable. They have become firmly fixed in their sockets, and their character is quite changed. They are of much larger size, approach nearer to each other at their base; and, instead of being rounded at their apices, they terminate in a strong rostrate point. No longer used as eyes, they now assume the functions of a rostrum; while the true rostrum, so conspicuous in the southern specimens, has, marvellous to state, become absorbed. Had there been only a single example of this form procured, we should at once have concluded that we had found a monstrosity; but there is no room for such an hypothesis by which to escape from this most strange instance of modification of structure under altered conditions of life. Three specimens were procured, on two different occasions, and they are in all respects similar.” Specimens of these crabs found in _shallow_ water had perfect eyes; but, beyond one hundred and ten fathoms, they had changed as above stated. As Darwin has said, the stand for the telescope is there, though the telescope with its glasses has been lost. Probably many of the deep-sea forms are luminous in some way.[40] _Aristeus_ and allied forms are known to have phosphorescent eyes. Others have phosphorescent organs in various parts of the body. In one, the legs bear luminous bands that sparkle and gleam as the animal moves along in its dismal home. In others there are certain globular luminous organs beneath the thorax, and between the abdominal swimmerets that have been described as eyes. The light emitted by the several organs is of different degrees of brilliancy.