688 



DEPTHS OF THE OCEAN 



to enable us to find all degrees of light-intensity, at all events 

 during summer. Pm^a/iparis bathybii, 

 the large black bathypelagic fish found 

 by us in the Norwegian Sea (see Fig. 

 107, p. 127), possesses well-developed 

 eyes, although it lives in deep water 

 and undoubtedly in surroundings just 

 ^ as devoid of daylight as does Cyclo- 

 ^ tJione microdon. The same remark 

 I applies to RJiodichthys regina. 

 '^ Is it the rich phosphorescent pel- 



E agic fauna peculiar to the coast waters 

 ^ and the boreal area which renders 

 « light-organs useless and eyes useful to 

 ? the fishes of these regions? Is it the 

 * case that the peculiar light-organs and 

 I the wonderful eyes can develop only 



in warm oceanic waters of low specific 

 I" gravity ? Are all these features only 

 Z special adaptations to special and 



1 1 definite conditions, like the splendid 



^'^ colours of animals in tropical lands .f* 



I ;f Are the small light -organs and the 



° minute organs of vision peculiar to the 



^ deep, dark, and cold oceanic waters 



1 only rudimentary organs, which are no 

 . longer of vital importance to the fishes? 



■a Are they to be considered as evidence 

 '^ that these fishes are descended from 

 ^- ancestors living under entirely different 

 I conditions in lesser depths ? 



I Floating and Organs of Floating 



I If organisms did not possess the 



c^ power of floating, thus preventing them 

 from sinking into deep water, the ocean 

 would become a lifeless desert, be- 

 cause in the surface layers of the ocean 

 live the minute plants which form the 

 source of nourishment for all animals 

 in the various depths of the ocean. 

 In order to understand the faculty of floating possessed by 



