Color Discrimination in the Gray Snapper. 



277 



4 minutes, 3 trials were made in whicli a clioice was offered of blue and 

 yellow. The blue atherinas were prepared as in experiment 26 and were of 

 a shade equivalent to a gray containing- 65 per cent black. The yellow 

 fish were stained in Diamond package dye, fast yellow, according to direc- 

 tions on the package. It was equivalent in brightness to a gray containing 

 53 per cent of black. The fish of both colors had been treated with acetic 

 acid in the staining and were therefore of like taste. They were of the 

 same size and all, except one yellow, floated. The result of the experiments 

 is shown in table 6. I was unable with the materials at command to obtain 

 a yellow darker than the blue. The snappers in all three colonies had, 

 moreover, now become so familiar with the un])alatabilitv of colored formalin 

 fish that further experiments with them could not be made. When it is re- 

 membered that in the red-blue experiments the snappers discriminated be- 

 tween the atherinas on account of their color tone, not on account of their 

 brightness, and that in the green-blue experiments they fail to discriminate 

 on account of brightness, it seems to me that in spite of the small number of 

 atherinas included, table 6 shows clearly a power of discrimination between 

 the blue and yellow used. The experiment includes 3 trials of 10 fish each 



5 blue, 5 yellow. 



Table 6. Total number of blue and yellow atherinas taken in each order by a colony 

 f 150 gray snappers at the Laboratory dock, July 26, 1907. 



* I blue and 3 yellow remained untaken in the last throw and are not included in the table, 

 which therefore includes 26 fish instead of 30. i yellow remained untaken in the first throw and 

 4 in the second; these are included in the table as though taken after the blues of their respective 

 trials. 



Here again the behavior of the snappers was even more conclusive, as the 

 following extract from my notes, referring to experiment 29, shows : 



After feeding on blue for some time (3 or 4 minutes) they were offered 

 blue and }ellow in lots 10 (5 each). A distinct preference developed for 

 the blue. The snappers showed little interest in the yellow, leaving fish of 

 that color largely unnoticed, but swimming about under the blue until finally 

 taken. One yellow sank and was examined perhaps 50 times by various 

 snappers, but remained untaken on the bottom. The yellows were left for 

 the most part apparently unnoticed, but when one was approached the fish 

 jerked back from it. All besides myself who watched the experiment agree 

 that the behavior of the fish shows more clearly than the actual record that 

 they discriminate yellow and blue. This colony had had no previous experi- 

 ence with vellow atherinas. 



