ADAPTIVE CHANGES OF COLOR AMONG FISHES 



By F. B. Sumner 



Perhaps I owe an apology for coming before this meeting 

 with a discourse which bears so httle relation to practical 

 fisheries problems as this one on the color-changes of fishes. 

 It is to be presumed, however, that the fish culturist and the 

 angler have observed some of the phenomena which I am 

 about to describe and have perhaps even realized in a 

 ^general way their meaning. And I think you will agree with 

 me that the man who takes an intelligent interest in his 

 stock — be it fishes or cattle — is a far more practical man, 

 in the broad sense of the word, than the man who confines 

 himself to the ordinary routine duties of his profession. 



That many fishes are strikingly adapted to their sur- 

 rounding in respect to their general coloration is a fact 

 familiar to all. A casual inspection of any good aquarium 

 will reveal abundant instances. It has likewise long been 

 known to naturalists that certain species possess the power 

 of changing their colors with more or less rapidity in con- 

 formity to changes in the color or the shade of the back- 

 ground. Those, for example, who have had much to do 

 with the common minnow, Funduhis, in our laboratories at 

 Woods Hole, realize that this fish is far paler when kept in 

 a white vessel than when kept in a dark one. The work of 

 Pouchet and of a number of subsequent investigators has 

 shown that the stimuli which call forth these changes are 

 received through the eyes, since blinded fishes no longer 

 respond adaptively. Such fishes may, it is true, undergo 

 changes of color, but these changes have no relation to the 

 optical properties of the environment. And, indeed, normal 

 fishes may undergo rapid changes of color, as a result of 

 what have been called "psychic" stimuli, e.g., fright, sexual 

 excitement, etc. Thus Dr. Townsend has recently published 

 some interesting articles in which he has described and 



