THE GREAT DEEPS 131 



on a cylindrical stalk, so that they are fitted 

 for making the most of a dim light. 



Two answers to the question are possible. 

 The first is, that though the animals with 

 large eyes have been dredged up from the 

 great depths, and probably spend most of 

 their time there, they may sometimes migrate 

 far enough upwards to come within the sun's 

 influence, and it is only if the eyes are never 

 used at all that they tend to dwindle away. 



The second answer is, that though there is 

 no daylight, there is some light from lumi- 

 nescent animals. Perhaps it is this uncertain 

 light which the big eyes use. 



Perhaps one of the biggest puzzles is that 

 the ordinary activities of life, such as diges- 

 tion and breathing, seem to go on quite 

 smoothly in the great deeps, although the 

 conditions of life are so very different from 

 those to which the shallow-water relatives of 

 the abyssal animals are accustomed. 



ORIGIN OF DEEP-SEA ANIMALS 



Where did the deep-sea animals come from? 

 This is a good question, but we do not yet 

 know enough to be able to answer it as we 



