AMONG SOME OP THE LOWER ANIMALS. 123 



I may add that the blue and violet divisions \Yere naturally- 

 longer than the red and green. 



May 25. — Tried again the same arrangement, but separating the 

 yellow, and giving the Daphnias the choice between red, yellow, 

 green, blue, violet, and dark : — 



Dark. Violet. Blue. Green. Yellow. Eed. 



Exp. 1 3 39 5 3 



„ 2 1 2 37 7 3 



„ 3 4 31 10 5 



„ 4 1 5 30 8 6 



„ 5 1 4 33 6 6 



3 18 170 36 23 



Of course it must be remembered that the yellow band is much 

 narrower than the green. I reckoned as yellow a width of -| inch, 

 and the width of the green 2 inches. 

 Again 



Dark. Violet. Blue. Green. Yellow. Bred. 



Exp. 1 4 30 6 10 



„ 2 1 3 25 8 13 



„ 3 2 24 9 15 



„ 4 1 3 25 8 13 



„ 5 1 2 24 7 16 



1 2 14 128 38 67 



M. Paul Bert observes (/. c.) that in his experiments the 

 Daphnias followed exactly the brilliance of the light. It will be 

 observed, however, that in my experiments this was not the case — 

 as there were m.ore Dapbnias in proportion, as well as absolutely 

 in the green, although the yellow is the brightest portion of the 

 spectrum. 



I then so arranged the trough that the yellow fell in the middle 

 of one of the divisions. The result was : — 



Number of Daphnias. 



Upper edge 



Ultra-red of red, Greenish 



and yellow, and blue and Ultra- 

 lower red. lower green. blue. Violet. violet. 



Exp. 1 8 38 4 



„ 2 9 36 5 



„ 3 8 39 3 



9* 



