448 GEETRUDE MAREAN WHITE 



Warning coloration. There seems to be no valid case of warn- 

 ing coloration in any animal fed upon by fishes. Reighard 

 ('08) tried to discover whether the conspicuousness of coral-reef 

 fishes might not have this significance. He found that the gray 

 snapper could be taught to avoid snapping at red fishes when 

 they were treated so as to be unpalatable, but that when none 

 were artificially treated the gray snapper devoured all species 

 of coral-reef fishes with the same avidity. Longly ('17) rejects 

 the hypothesis of warning coloration as accounting for the bright 

 colors of coral-reef fishes. 



Choice of colored lights and backgrounds. The method has 

 been tried of illuminating different parts of an aquarium con- 

 taining fishes with lights of different colors, or of placing va- 

 riously colored papers or glasses under or around the aquarium. 

 The fishes are allowed to choose the part of the tank they prefer. 

 The chief difficulty with this type of experiment is that unless 

 spectral light is used the colors are not pure, and it is extremely 

 difficult to obtain lights of various wave-lengths which have the 

 same luminosity. Pigmented papers have not been made 

 which will reflect light of a single color. 



The first experiments relating to color discrimination were 

 performed, by Graber ('84), who used glass slides of different 

 colors. Such screens were not 'pure,' but allowed light of va- 

 rious wave-lengths to pass through. Although the fishes Cob- 

 itus barbatula and Alburnus spec, showed decided preferences 

 for red, there is little to indicate that the choice was necessarily 

 due to the length of the fight waves. 



Bauer ('10) reports a difference between light and dark 

 adapted fishes. Light adapted Charax puntazzo and Atherina 

 hepsetus avoided a light shining through a red filter 680^ to 710^, 

 but when ' dark adapted' these fishes prefered red to blue, which 

 Bauer considered to be of the same intensity. These observa- 

 tions were interpreted to mean that fishes are able to recognize 

 colors, but that when they are 'dark adapted' color perception 

 of the red end of the spectrum ceases much sooner than for nor- 

 mal human eyes. 



