702 



Comparative Animal Physiology 



strong activity in black-pigment dispersal and simultaneously leave white 

 pigment dispersed or induce its dispersal. Extracts of connectives, on the 

 other hand, produce only a weak black-dispersing action but cause concen- 



Fig. 268. A, Relationship between time and melanophore state in Ligia after transfer 

 from a black to a white background and vice versa. B, Changes in melanophore state after 

 transfer from darkness to black and white backgrounds, and vice versa. C, Relationship 

 between portion of Ligia eye stimulated and the average melanophore state. The illum- 

 inated portion of the eye is black. From Smith."' 



tration of the white pigment. The differing results cannot be duplicated 

 simply by varying the concentrations of nervous system extract. Although 

 these observations establish the presence of two chromatophorotropins, they 



