236 Fortieth Annual Meeting 



illustrated the color changes that he has observed among 

 the fishes in the tanks of the New York Aquarium. And it 

 is likely that most of the fish culturists present today have 

 noted cases where a sudden and conspicuous change of color 

 has resulted from a fish having been handled or otherwise 

 disturbed. Such changes do not, however, have any 

 adaptive significance so far as we know. They are probably 

 of no more utility to the animal than are blushing and 

 various other indications of emotional disturbance in 

 ourselves. 



It now seems to be fairly certain that the color changes 

 of fishes are brought about by a movement of the pigment 

 granules within the chromatophores or color cells of the 

 skin, and not by an actual contraction and expansion of 

 the chromatophores themselves. The work of Pouchet and 

 others has shown that the efferent nerve tracts which control 

 this action of the color cells pass through the sympathetic 

 trunks. Section of the spinal cord alone will not result in 

 a paralysis of the chromatophore function below this level ; 

 section of the sympathetic chain will do so. But just as 

 muscle or gland cells may be called into activity by stimuli 

 applied directly, without the intervention of nerve fibers, so 

 the chromatophores may be caused to contract by tactile 

 stimuli or by the electric current. 



Such, in brief, are the main facts which have been 

 recorded regarding the physiology of color changes among 

 fishes. It is my purpose today to discuss certain experi- 

 ments which I conducted at Naples * during the past winter 

 and which I have continued during the present season at 

 Woods Hole. 



As is frequently the case with those who visit the Naples 

 station for the purpose of biological investigation, I failed 

 to find material suited to the problem upon which I had 

 originally expected to work. I therefore said to myself: 

 "So much the worse for your problem," and set about to 



*I take pleasure in acknowledging the facilities and courtesies ex- 

 tended to me by the director and staff of the Naples station. 



