LIFE IN GREAT DEPTHS 155 



enormous pressure must inevitably cause the violent 

 explosion of a fish rapidly raised to the surface. 



From a private letter from the eminent American 

 zoologist Rolf Bolin, whom I was fortunate enough to 

 meet in San Francisco after his return from the 

 "Galathea" Expedition, I am allowed to quote the 

 following passages of special interest for the preceding 

 as well as the ensuing remarks. 



"I know of no real deep-sea fish which has an air- 

 filled swimbladder. This organ either drops out entirely 

 or is modified into a fat-storage organ. The first men- 

 tion of the latter condition I know of was published 

 about three years ago, so there is not much literature 

 on the subject. . . . 



"With the tendency to a loss of eyes in deep-sea 

 forms, there has come a concomitant development of 

 other sense organs. In some cases the impression of the 

 surroundings is gained through tremendously enlarged 

 olfactory organs. In others the 'lateral line' is astonish- 

 ingly developed, so that the fish can 'hear' things around 

 it; and in still others long filaments, developed from 

 extended fin rays or from barbels, are used to pick up 

 vibrations in the water. All of these, however, are to 

 be found just as commonly in depths of about 3,000 

 meters as in the great depths." 



Most fishes from great depths are of slender build 

 and because they lack powerful muscles are not very 

 good swimmers. On the other hand they are in general 

 provided with very big mouths and highly distensible 



