ABYSSAL BENTHAL AND PELAGIAL 



261 



ment of the organs of touch and smell is found in cave animals (cf. 

 Chapter XXVII). 



Coloration in relation to illumination. 22 — The protective colora- 



a 



Fig. 71. — Telescopic eyes of deep-sea fishes of various families: a, Argyro- 

 pelecus affinis; b, Gigantura chuni; c, Winteria telescopa. After Brauer. 



tions of the animals of the lighted benthal have been discussed above 

 (p. 188). They are extremely varied, in correlation with the variety of 

 background on which the animals live. The colorations of pelagic ani- 

 mals in the lighted zone are much less varied. The plankton animals 

 are in the main transparent, in part owing to the high water content 



Fig. 72. — Bathypterois longicauda from 4600-m. depth in the south Pacific. 



After Gunther. 



of their bodies. For the rest, blue is the dominant color, as in the 

 siphonophore Velella, on the edge of the disk of the medusa Rhizo- 

 stoma, in the copepod Anomalocera, the decapod Virbius, and in the 



