PERCEIVE DIFFERENCES OP COLOR. 231 



13 under the blue. After seven observations, during 

 which 86 were added to the yellow, 263 to the red, and 

 272 to the blue, the numbers were — under the yellow, 

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



Yellow. Ked. Blue. 



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 brillianfy beyond which the lii^ht 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, 1 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. 

 12 



