PEKCEIVE DIFFERENCES OP COLOR. 



231 



13 under the blue. After seven observations, during 

 which 8Q were added to the yellow, 263 to the red, and 

 272 to the blue, the numbers w^ere — under the yellow, 

 38 ; under the red, 13 ; and under the blue, 15. 



Yellow. 



Red. 



Blue. 



First observation. 



At the beginning 

 „ end 

 Second observation. 

 At the beginning 

 „ end 

 Third observation. 

 At the beginning 

 „ eud 

 Fourth observation. 

 At the beginning 

 „ end 

 Fifth observation. 

 At the beginning 

 „ end 



I conclude, then, that the presence of some of the 

 Daphnias in the red, blue, and violet is more or less due 

 to the causes above indicated, and not to any individual 

 preference for those colors. 



My experiments, I think, show that, while the Daph- 

 nias prefer light to darkness, there is a certain maxi- 

 mum of brilliancy beyond which the light becomes 

 inconveniently bright to them, and that they can 

 distinguish between light of different wave-lengths. 

 I suppose it would be impossible to prove that they 

 actually perceive colours ; but to suggest that the rays 

 of various wave-lengths produce on their eyes a different 

 impression from that of color, is to propose an entirely 

 novel hypothesis. 



At any rate, I think I have shown that they do 

 distinguish between rays of different wave-lengths, and 

 prefer those which to our eyes appear green and yellow. 



