ADAPTIVE CHANGES IN COLOR OF FUNDULUS. 63 



that fishes in the yellow box showed a decidedly yellow color while 

 those in the white box which reflected all light, were pale. Al- 

 though the melanophores or black pigment cells by their contrac- 

 tion or expansion due to intensity, indirectly influence the color 

 to some extent by exposing or covering other color elements of the 

 skin, the resulting effect of each colored background cannot be 

 lained by this factor. The specific effect is due to color or 

 wave-length. 



It wa- tir-t proved by Pouchet (18/6) and later by von Frisch 

 (1911) and other investigators that the expansion of the chromato- 

 phores is 'I'd by the sympathetic nervous system; the eyes 



ai t for the stimuli that cause changes in shade and 



color. I ; "r when the fish were blinded, no adaptive change in 

 -had.- or "'l<>r took place. In the experiments on Fundulus, col- 

 ]<lioii made opaque with lampblack was placed over the eyes and 

 i by stitches of silk thread sewed into the superficial skin. 

 Tln-M- c. .ll.idion caps generally remained on for a few days, suffi- 



tly long to show that no adaptive change in shade takes pi. 

 when tish are blinded, but not long enough to sbow that adaptive 

 coloration is likewise controlled through the medium of the eye, 

 as has 1,,-cii established by investigators for other species. Other 

 method- were employed but the shock of operation caused changes 

 in color and shade which made the specimens useless for purposes 

 of safe comparison. 



Finally it was found that making the cornea opaque with a 

 heated needle had no perceptible influence on the healthy condition 

 ;he fishes. Specimens so treated were allowed to remain 

 for a couple of days in order to make sure of their otherwise nor- 

 mal condition before being placed with other fishes in the differ- 

 ently colored backgrounds. In each case the blinded animal 

 showed n -inuilation of the background. 



It i- an error to assert, as has been done by some, that blindness 

 neccssariK causes maximum darkening of the fish. It depends 

 on the method and length of operation, and different degrees of 

 darkening can be obtained almost at will. The possible objection 

 that making the cornea opaque might still permit the eye to receive 

 the stimuli!- and thus account for lack of darkening is met by the 

 fact that fishes thus blinded maintain a light shade if placed in 

 5 



