76 CORA D. REEVES 



color of the male probably plays no role in selection by 

 the female Elheostoma coeruleum (Reeves 1907), but that 

 displays of the male may nevertheless play a part in the 

 breeding activities. The color of the breeding fish need 

 not indicate the presence or absence of color vision in a 

 given species, but the absence of ability to distinguish 

 wave-length can not be demonstrated by assuming or by 

 proving that the red wave-lengths do not penetrate to the 

 breeding grounds of any species. (See also postscript.) 



Hess (1913) showed that if the integument of young 

 eels is subjected to the action of violet light, a peculiar 

 fluorescence appears. He did not find this when he used 

 older fish. I found that a certain very large sunfish (not 

 the one whose graph is shown in fig. 15) failed to learn to 

 discriminate a blue and red which the smaller sunfish, SS2, 

 discriminated. This may have been due to a difference 

 in effect of light on the retinas of young and old sunfish 

 comparable to the difference in effect of light on the inte- 

 gument of young and old eels. It may also have been due 

 to greater readiness of the younger fish in forming a sen- 

 sory habit. 



Before leaving the work of Hess, it may be well to char- 

 acterize it in more general terms. The conditions of his 

 first work, which was carried out in the dark, were unfavor- 

 able for observing small differences in behavior. His sub- 

 sequent failure to find color vision is in part due to the 

 earlier failure, in part to the fact that he worked often in 

 the dark, and in part to his method of handling the fish. 

 Small differences in behavior are difficult if not impossible 

 to observe under the conditions of illumination he used. 

 His method of handling his fish introduces too many dis- 

 turbing factors. Fish picked up and put into the light and 

 then put into the dark will show excitation or inhibition 

 effects because they are especially sensitive to jarring and 

 shifting of the aquaria. But differences between response 

 to red and other colors exist; and Hess found these and 

 misinterpreted them. His work in establishing the simi- 

 larity in brightness values of different spectral regions for 

 fish and for the totally color-blind will probably be con- 

 firmed. 



