226 EVIDENCE THAT DAPHNIAS 



perhaps too dark ; I took, tlierefore, a lighter tint, and 

 rearranged my little apparatus as follows : — 



I placed (March 26) fifty Daphnias in a trough (1), 

 covering over one half of it with a pale green, and 

 another fifty in a trough (2) half of which was covered 

 with yellow (aurine). On one side was a similar trough 

 (3), one end of which was shaded by a porcelain plate ; 

 and on the other side a fourth trough (4), one end of 

 which had a little, though but little, extra light thrown 

 on it by means of a mirror. As before, I counted the 

 Daphnias from time to time, and turned the troughs 

 rjDund. All four were in a light room^ but not actually 

 in direct sunshine. Thus, then, in one trough I had 

 half the water in somewhat green light ; in the second 

 trough, half the water in yellow light; in the third, 

 one half was exposed and the other somewhat darkened ; 

 while the fourth, on the contrary, gave me a contrast 

 with somewhat more vivid light. If, then, the 

 Daphnias went under the green and yellow glass, not 

 on account of the color, but for the sake of shade, 

 then in trough 3 a majority of them would have gone 

 under the porcelain plate. On the other hand, if the 

 porcelain plate darkened the water too much, and yet 

 the open water was rather too light for the Daphnias, 

 then in the fourth trough they would, of course, have 

 avoided the illuminated half. The results show that 

 the third trough was unnecessary, still, I may as well 

 give the figures ; the fourth proves that the Daphnias 

 preferred a light somewhat brighter than the ordinary 

 diffused light of the room. Of course, it does not follow 

 that the effect of color is the same as with us. 



