410 FKANCIS B. SUMNER 



The work of Pouchet- and a number of subsequent investi- 

 gators has shown that the stimuli which call forth these responses 

 are received through the eyes, since fishes which have been de- 

 prived of their sight no longer change adaptively. Blind fishes 

 may, it is true, undergo changes of color, but these changes bear 

 no relation to the optical properties of the environment. And in- 

 deed normal fishes may exhibit rapid changes of color, as a result 

 of what have been not very appropriately called 'psychic' stimuli, 

 e.g., fright, sexual excitement, etc. Thus Newman^ has given us 

 an account of the play of colors in Fundulusmajalis during 'court- 

 ship' and Townsend^ has described and figured the color changes 

 which he has observed in fishes of a number of species in the New 

 York Aquarium. But changes such as these do not, so far as 

 we know, have any adaptive significance whatever. 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 immediate cause of 

 the color changes of fishes, as well as those of many other animals, 

 is a movement of the pigment granules within the chromatophores 

 of the skin, and not an actual contraction and expansion of the 

 chromatophores themsevles. The work of Pouchet, Van Rynberk^ 

 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 sympa- 

 thetic chain will do so. But just as muscle or gland cells may be 

 called into activity by stimuh applied directly, without the inter- 

 vention of nerve fibers, so the chromatophores may undergo a 



2 The most important of this writer's contributions to the antomy and physiology 

 of the chromatophores are presented in the "Journal del'Anatomie et de la Phys- 

 iologie," 1876, pp. 1-90 and 113-165. 



3 Biological Bulletin, April, 1907. 



■^Thirteenth Annual Report of the New York Zoological Society, 1909. 



5 Van Rynberk (Ergebnisse der Physiologie, Bd. 5, 1906) presents copious ab- 

 stracts of the work of the principal previous investigators in the field of color 

 change among animals; likewise what seems to be a fairly exhaustive bibliography 

 of the subject up to the date of his publication. For this reason, I have not thought 

 it necessary to cite many of these earlier papers myself. 



