284 Papers from the Marine Biological Laboratory at Tortugas. 



Since in the color-discrimination experiments 30 and 31, the snappers 

 preferred the white to the blue and the blue to the red, they choose in the 

 first case the brighter fish and in the second case those less bright. They 

 were therefore guided not by the brightness of the fish, but by their color. 

 Had time permitted and material been available the experiments of 1905 

 with fresh atherinas would have been extended so as to include a red-blue 

 series in which the red was the darker color. Other colors would also have 

 been used. 



DISCUSSION OF COLOR DISCRIMINATION EXPERIMENTS. 



The colors used in the experiments described were obtained by the use 

 of dyes. They are impure, and I know of no dyes by which pure spectral 

 colors may be obtained. The red used shows with the spectroscope rays of 

 all wave-lengths below the green, while the blue shows waves of all lengths 

 above the yellow. The yellow used is nearly pure, the green includes both 

 yellow and blue rays. We may therefore conclude that the snappers dis- 

 criminate between a mixture of colors of that part of the spectrum which 

 lies below the green and a mixture of the colors of that part which lies 

 above the yellow, and that they discriminate yellow from a mixture of the 

 colors of the part of the spectrum above the yellow. Whether the particu- 

 lar mi.xtures used appear to the snapper as they do to us, we can not know 

 from the experiments. On the other hand, these mixtures may appear to the 

 snapper precisely as thev do to us and his power of color discrimination may 

 be as accurate for all colors as our own. The only paper known to me on 

 color discrimination in fishes is that of \\'ashl)urn and Bentley ( 1906). where 

 results were obtained on a single individual of Scjnotilus atromaculatus. 

 The fish was kept in an aquarium and the methods were those of the labora- 

 tory. The results are in accord with my own. The literature of the subject 

 is discussed by Washburn and Bentley. 



VI. ESTABLISHMENT IN THE GRAY SNAPPER OF A WARNING COLOR 



REACTION, INVOLVING AN ASSOCIATION BETWEEN 



COLOR AND UNPALATABILITY. 



In the experiments described in this section red atherinas were rendered 

 unpalatable and were then fed to the Laboratory colony of gray snappers, 

 in order to learn whether the snappers would form an association between 

 the unpalatability of the atherinas and their color, of such a sort that they 

 would refuse the atherinas at sight, i. e., by reason of their color alone. 

 If this should prove to be the case the color red would have come to have 

 for the gray snapper a warning significance experimentally established under 

 normal conditions. 



In some of the preliminary experiments the red atherinas were rendered 

 unpalatable bv the use of substances not normal to the environment of the 



