The Fishes of the Deep Sea 55 



occasionally, when the depth is not great, with sea urchins, 

 or sponges, or scallops, or other shell-fish. Sometimes it 

 contains nothing at all, even after a laborious half day has 

 been given to a single operation. More often the naturalist 

 is rewarded by a few fishes, with crabs, sponges, sea urchins, 

 and sometimes in a single haul he captures very many. 



At the depth of a few hundred feet the fishes are usually 

 red in color, with very large eyes. At greater depths, they 

 are all of a uniform violet or inky black, and the eyes are 

 either excessively large or excessively small. The very 

 large eyes seem to represent an effort to make the most of 

 what little light there is. The very small ones are simply 

 vestiges, and mean that Nature has given up the idea of 

 letting her creatures see. A certain number of these deep- 

 sea fishes are provided with lanterns or luminous spots by 

 which they find their way in the great depths. All the 

 species thus provided have well-developed eyes. The lumi- 

 nous spots usually lie in rows along the side of the body. 

 In some forms the whole snout is luminous, like the head- 

 light of an engine. In the case of a Japanese deep-sea 

 sharklet, about a foot in length, the whole belly is luminous. 

 Of this species, Etmopterus lucifer, Dr. Peter Schmidt of 

 St. Petersburg, once made a sketch in the night by the light 

 given out of the animal itself. 



The deep-sea fishes are all descended by degeneration and 

 specialization from various tribes of shore fishes. The de- 

 generation involves loss of organs, the softening of the tis- 

 sues, both bones and muscles, and often the loss of fins or 

 scales. By the stretching of the tissues, a deep-sea fish may 

 often swallow another of considerably larger size. The 

 specialization consists in the great development of luminous 

 spots in many cases, the development of very long teeth in 

 most cases, and in occasional modification of fins as organs 

 of touch. 



Most of the luminous forms are of the group called lan- 

 tern-fishes, degenerated from allies of the smelt and trout. 



