Color Discriiiiinatioii in tlic Gray Siuif^f^cr. 



275 



order bv a colony of 100 gray snappers at the east lighthouse dock, Jiih- 24, 

 1907. The experiment includes a blue-light-rcd series of 5 trials and blue- 

 dark-red series of 6 trials each trial of 10 fish 5 blue, 5 red. The last 

 blue-dark-red trial of 8 fish only. lUue-light-red trials began at 10 a. m. ; 

 blue-dark-red at 4" 12 p. m. 



T.\BLE 4. 



This fish sank. , , , . , . , 



t All 5 reds of the first trial and 3 of the second were untaken; they are included in the table 

 as though talscn after the blues. 



In this experiment errors due to possible difl'erences in the chemical 

 properties of the fish of the two colors seem to be eliminated by the preser- 

 vation in formalin and by the use of acetic acid in staining ; errors of size 

 are eliminated by use of mature female atherinas of practically uniform size; 

 errors of position are eliminated by the random mingling of the blue and 

 red atherinas all floating at the surface. The snappers have clearly chosen 

 the more familiar blue in preference to both a lighter and a darker red. 

 Thus 21, or 84 per cent, of the blue fish are taken in the first 5 orders when 

 offered with light red, and but 4, or 16 per cent, in the second 5 orders; 

 26, or about 90 per cent, of the blue fish are taken in the first 5 orders when 

 otifered with dark red, while but 3, or 10 per cent, are taken in the second 5 

 orders. I can interpret the result only as showing blue-red color-vision. 



To an observer the behavior of the snappers is quite as convincing as 

 the tabulated data. Repeatedly when a blue and a red fish floated near one 

 another, but at some distance from other atherinas, a snapper after swimming 

 about beneath them for considerable time, as though examining both, took 

 the blue. If in any such case during this experiment the red fish was the 

 first of the two to be taken the fact escaped me. Repeatedly, too. snap- 

 pers approached red fish and then jerked back and did not take them, but 

 a similar behavior toward the blue was not observed. 



Experiment 28: Blue and green color discrnniiiotioii. V,y July 25. 1907, 

 all 3 colonies of snappers had become so experienced in atherinas preserved 

 in formalin that they took them slowly, and after taking a limited number 

 in any one experiment, refused them altogether. The remaining experi- 

 ments were thus necessarily each restricted to but few trials. 



On the afternoon of July 25 blue, prepared as in experiment 26, was 

 offered with both light and dark green, all made to float. The greens were 



