418 STELLA B. VINCENT 



Fish were kept for long periods in aquaria with double walls, 

 the spaces between being filled with Nagle's color solution, and 

 the same results were obtained. The blind fish were not affected 

 by the red or yellow background hence pigment growth is not 

 due to the effect of colored light. This work was demonstrated 

 before five people. Von Frisch thinks that the adaptation to 

 brightness does not depend upon light intensity alone but 

 also upon color contrast and is a higher reaction than that to 

 color as is proved by its quickness and its accuracy. He believes, 

 too, that the expansion of the red pigment cells is also, within 

 wide limits, independent of the brightness values of the bottom 

 and depends alone on its color value. 



The Hochzeitkleid is adduced as a strong bit of evidence of 

 the color vision of fish. Why, it is asked, should they take on 

 these brilliant colors at spawning time if these colors are of no 

 value in sexual selection. 



Von Frisch as well as Hess made experiments with colored 

 food. When his fish which had been trained for yellow food 

 were offered a series of gray papers together with yellow upon 

 a gray background, they always snapped at the yellow, he says, 

 and never at the gray. They chose red papers and not black 

 upon a gray ground. In this respect they differ from bees. They 

 frequently snapped at purple and yellow-green. He gives the 

 numbers of his papers and had the results demonstrated before 

 five people. He also fed his fish from a series of colored tubes 

 so arranged that food could be placed in the top and the tubes 

 sunk in the water. Phoxinus laevis could distinguish red-yellow, 

 green and blue from gray one and one-half centimeters below 

 the surface. The red and the yellow were confused. He explains 

 this by saying that the red pigment is essentially a sex color 

 but that later it functions in the same way as yellow. The 

 protective colors are on the back, the sex colors on the abdomen. 



Hess admits, as all must, the chromatic adaptation in fishes 

 but criticises its significance as a proof of color vision. He also 

 disputes some of von Frisch's facts and questions certain methods 

 which he uses. Some apparatus was constructed by Hess by 

 means of which two bowls containing fish could be lighted from 

 below with diffused lights of known strength. The observer 

 could not detect the slightest difference in the appearance of 

 the fish even when one light was five or six times the strength 



