ADJUSTMENT OF FLATFISHES 479 



A word in regard to the utility of this power of color change in 

 the hfe of the organism. Despite the recent reaction against 

 extravagant appUcations of the protective coloration principle, 

 it is difficult to doubt, in the present instance, either that this 

 faculty has some use, or that it has been developed in some way 

 because of its use. The end to be attained seems to be concealment 

 and nothing else. No appeal to thermal regulation,** to possible 

 '^photoreceptive" or "photosynthetic" functions of the skin 

 pigments, nor any other purely physiological explanation of the 

 phenomena seems adequate. A complete explanation must 

 regard ecological factors as well. Whether the utility of these 

 changes to the fish consists primarily in their concealing the latter 

 from its enemies or from its prey cannot, however, be stated with- 

 out a greater familiarity with the bionomics of these species than 

 the present writer possesses. I learn from several trustworthy 

 observers that flounders of various kinds are preyed upon by 

 sharks and other large fishes. The only information which I have 

 relating directly to the enemies of any of the species which have 

 been discufesed in this paper, is the statement of Mr. Vinal Ed- 

 wards that he has taken sand-dabs, along with other flounders, 

 from the stomach of the cod. It is quite probable a priori that all 

 of the species are similarly preyed upon. 



As regard the prey of these fishes^ I can but offer my own obser- 

 vation that specimens of Lophopsetta, when recently brought into 

 the laboratory, frequently regurgitated the 'sand-launce' (Ammo- 

 dytes americanus), sometimes in considerable numbers. It is 

 not unlikely, therefore, that the cryptic coloration of flounders is 

 of advantage in concealing them from smaller fishes '^^ until the 

 latter come within easy range. 



These few meagre statements of course illustrate the paucity of 

 our direct evidence upon the whole question of the utility of cryp- 

 tic coloration, and indicate the inferential nature of most of our 

 conclusions in this field. 



February 23, 1911. 



^^ As suggested by Max Weber et al. (Van Rynberk, op. cit., p. 568 et seq.) 

 *» Invertebrate food may perhaps be left out of consideration here. 



