THE CHARACTERS OF THE DEEP-SEA FAUNA 67 



known to live in deep water, and it might be added 

 that green is extremely rare as a colouring matter in 

 abysmal animals, although the phosphorescent light 

 given out by some of the echinoderms is green. 



Blue, as a colouring matter of marine animals, 

 living on the surface or in shallow water, is not un- 

 commonly met with, distributed in the form of bands 

 or stripes, but green is extremely common in fishes, 

 Crustacea and coelenterates, and it is a point of very 

 considerable importance that in this respect there 

 is a very great difference between the deep-sea and 

 the shallow-sea faunas. 



If a considerable collection of living abysmal forms 

 could be placed upon one table and a similar collec- 

 tion of shallow-water forms upon another, I believe 

 that the first general impression upon the mind of 

 one who saw them both for the first time would 

 be the presence of green colours in the last-named 

 collection, and the absence of it in the other. 



The eyes of the animals that live in deep-sea 

 water undergo curious modifications. If the fauna 

 of the abysmal region were confined to conditions of 

 absolute darkness, we should expect to find either a 

 total absence of eyes or mere rudiments of them only 

 in those forms that have recently migrated from 



F 2 



