n] 



HABITS OF CONVOLUTA 



47 



Mysis station themselves on the black part of a dish 

 the bottom of which is half black, half white. The 

 chameleon shrimp, Hippolyte varians, on the con- 

 trary, selects the white ground (Fig. 10). A similar 

 behaviour is exhibited by various fishes, trout among 

 others. 



1 I 



Fig. 11. Phototropism of C. paradoxa : the influence of background 

 on phototropic response. The flat, porcelain troughs containing 

 the animals are represented (in plan) by the oblongs. The bottom 

 of each trough is half white and half black. In the diagram, the 

 white ground is indicated by the unshaded, the black ground by 

 the shaded part of the oblong. The animals are represented by 

 dots, and arrows show the direction of the light. a. In bright 

 light, b. In weak light. c. "Choice" of black ground in 

 preference to white ground. 



So striking is the behaviour with respect to 

 background both of C. roscoffensis and C. paradoxa, 



