72 CORA D. REEVES 



did not confuse with the color any intensity of a long series 

 of grays varying from white to black, he decided that 

 their response had been to wave-length and not to bright- 

 ness. He further tested their color vision by seeing whether 

 the fish trained to go to a given color would respond to it 

 positively when other colors of matched brightness were 

 presented. He found that blue and green were discrimin- 

 ated from each other and from other colors as well as from 

 the grays of the series, but that the fish confused yellow 

 and red with each other though not with grays or with 

 black. 



Uhlenhuth (1911) after a critical and illuminating review 

 of the literature, accepts as conclusive Frisch's evidence 

 that fish react differently by color change to lights of dif- 

 ferent quality but of equal brightness. It does not follow 

 that they are aware of the color differences in their back- 

 grounds. Where a method of choice is used, as in my 

 own work, it becomes probable that the fish are stimulated 

 by quality and not intensity alone and that the quality 

 determines their choice, (cf. Mast 1916.) 



Frisch (1913) fed fish upon yellow-colored meat until 

 the habit of approaching it was fixed; then he tested them 

 by substituting colored papers for the meat. For these 

 tests small pieces of yellow paper were pasted upon sheets 

 of gray of the same texture. These gray backgrounds 

 included one the brightness of which matched that of the 

 yellow paper for his dark-adapted eye. Upon each gray 

 background, in addition to the yellow bit of paper, was 

 pasted one of similar shape of a darker gray and another 

 of a lighter gray. When these sheets of gray were placed 

 against the walls of the aquarium, the fish that were used 

 to the yellow food swam more frequently to the yellow bits, 

 while fish that had not been fed with yellow meat swam 

 with equal frequency to all three pieces of paper. From 

 this Frisch maintained his previous conclusions, that for 

 fish yellow and red light are different from white and from 

 other colors. 



Hess (1912) resumed his attack on the problem and 

 followed the method used by Frisch. He placed his fish 

 in a rectangular aquarium and fed them on yellow meat. 



