ADJUSTMENT OF FLATFISHES 461 



and Valette." The gray paint used was not perfecth^ neutral, it is 

 true, being, when fresh, sUghtly tinted with blue. After exposure 

 to sea-water, however, it changed somewhat, becoming 'warm' 

 {i.e., sUghtly yellow) instead of 'cold.' It was probably in this 

 condition during most of the period of the experiments. «*^ 



The gray box was situated near the window and was well 

 lighted throughout much of the day, though not exposed to direct 

 sunlight. 



Another box was painted white within, but its interior was 

 rather heavily shaded by a tent-shaped contrivance of gal- 

 vanized iron. This was painted black within, and had a long 

 cleft in the top, partly for the admission of light, partly to permit 

 of observations. The cleft w^as largely closed by strips of wood, the 

 amount and distribution of the light being thus controlled. 



No photographs were taken of the surfaces upon which the 

 fishes lay, but I feel sure that the difference in the amount of hght 

 reflected from the two bottoms was as great, or greater, than in the 

 experiment with Rhomboidichthys. 



Four fishes were used in the present experiment. Two speci- 

 mens at once were kept in each of the two boxes. From time to 

 time, those from one box were transferred to the other box, for 

 brief periods, in order that all four might be compared directly 

 under identical conditions of illumination and of background. 

 Such direct comparisons were also made with other pale fishes kept 

 in a neighboring white tank which was well lighted. 



At the close of the first phase of the experiment, the two speci- 

 mens in the gray box were found to be decidedly darker than 

 those in the shaded white box. More pigment was visible in the 

 skins of the former than in those of the latter, and they were of a 

 gray appearance, in contrast to the yellowish or slightly pinkish 

 appearance of those in the white box. The latter, moreover, were 



" Prof. Yerkes, who kindly matched a sample of this paint upon a color wheel, 

 reports that 75% of black and 25% of white gave the desired shade. 



^8 If anyone wishes to maintain that this slight element of color (aside from 

 shade) probably played some part in the results, I cannot absolutely refute him. 

 I can only say that my experiments as a whole make this seem to me highly improb- 

 able. 



