ADAPTIVE CHANGES IN COLOR OF FUXDULUS. 6l 



black-lined boxes illuminated by different monochromatic lights. 

 The different monochromatic lights have the same effect as white 

 light on a black background. 



Parker and Lanchner (1922) suggest the hypothesis that con- 

 trast rather than simple vision is involved in responses of this 

 kind. Keeblc and Gamble (1904) state that the shade assumed 

 by crustaceans depends on the ratio of light received by the eyes 

 directly from the source, and that received after reflection from 

 the ba< -k.^ri'iind. Summer (1910) believes that this ratio holds 

 good for fishes. Mast (1916) carried out experiments to test 

 this hypothesis and concluded that while simulation of back- 

 ground is not controlled solely by light reflected from the bottom, 

 the results of the experiments " throw considerable doubt on 



tllf ll\]>"! 



\Y< ' ave made no tests to determine whether the shade depends 

 iti't. The experiments merely indicate that the back- 

 ground laru'ly determines the shade. The slight differences in 

 sha 'hose colored by different monochromatic light is prob- 



:iltly due to diiTerent amounts of light passing through the filters, 

 and that lights of all colors had a stimulating effect just as white 

 li-ht in causing partial or total contraction of the black pigment 

 cells or im-lanophores. 



in these experiments the conclusion cannot be drawn that 

 it is <|uality and not quantity of light that determines the shade. 

 The uu-laiiophores expand and contract with comparative rapidity 

 in liijit of different intensities, and as no adaptive coloration was 

 .il.siTvl in these 24-hour tests the shade assumed was more 

 \-iltly it -ulatcd by the different intensities of the various mono- 

 chromatic lights. 



III. ADAPTIVE CHANGES IN COLOR. 

 A. Effect of Colored Backgrounds. 



In order to test whether Fundulns simulates the background 

 in color as some other species had been shown to do, the fishes 

 were placed in battery jars and set in boxes lined with the same 

 red papers as in the first series of experiments. Here, how- 

 ever, the boxes with the contained fishes were placed with the 

 open side facing the windows of the laboratory and subjected to 



