ADAPTIVE CHANGES IN 7 COLOR OF FUXDULUS. 71 



were equally dilated in fishes adapted to other environments, but 

 that the vessels were covered with melanophores. This seemed 

 to be true of the blue adapted fish, for the dorsal region showed 

 dark lines as if the melanophores were especially abundant and 

 expanded over the capillaries. But the anterior portion of the 

 head, where few melanophores are present, failed to show any 

 dilation. Again, the fishes adapted to a yellow background where 

 melanophores are maximally contracted and likewise those adapted 

 to a white barken >uiid where both melanophores and xanthophores 

 are contracted, showed no evidence of vaso-dilation. 



E. Green Adapted. 



In those adapted to the green environment, the shade was darker 



than in the preceding cases, due to partial expansion of the melano- 



phores. Tin- xanthophores were only slightly expanded. The 



most striking portion of the body in which this color was empha- 



!. \\TI- above the eyes. 



F. Blue Adapted. 



In t IK-SI- >pec miens the melanophores lying in the deeper por- 

 tion.-, df the integument, and those lying upon the proximal por- 

 tion of the scales were expanded, thus giving a grayish tone when 

 :i through the overlying adjacent scales. On the distal portion 

 of the -i-ale^. the melanophores were generally contracted. The 

 xanthoplmre> were maximally contracted thus exposing the blue 

 P-I! layer. When the surface of the skin was examined by 



retorted light, the predominant color coming from the brilliant 

 points was a bluish green. 



V. DISCUSSION 



in the brief outline at the beginning of this paper of the 

 more recent work on the problem of simulation of fishes to the 

 I. ark- round, it is evident that the majority of investigators have 

 found that the various species tested, do simulate the background 

 and <!IM Timinate light of different wave-lengths. To these species, 

 Fnndidns can unquestionably be added. 



Mast (1916) who made a detailed study of two species of 

 flounders and observations on other fishes kept in the aquaria at 



