426 Mr. Poulton's//Arf//6'/- experiments upon 



These results entirely harmonize with those obtained 

 in the other set of conflicting colour expariments applied 

 to dorsal and ventral areas. The rather leas dark pupoe 

 fixed to the white surface are to be accounted for by 

 the greater proximity of white enabling it to neutralize 

 the influence of the more distant black more completely 

 than when their relative proximity was reversed. But 

 even under the most favourable conditions, the white 

 surface did not produce nearly so great an effect as the 

 black. There were no particoloured pupae, and no 

 evidence that the ventral surface differs from the dorsal 

 in sensitiveness. 



In these experiments we meet with evidence that the 

 larvffi sought black in preference to wdiite surroundings, 

 when placed under the same conditions, and that they 

 also manifested a tendency to seek the side turned to- 

 wards the light. When both these causes co-operated, 

 viz., when the black surface was turned towards the 

 light, at least 19 out of 23 pupated upon it ; when they 

 were antagonistic, about half the larvffi followed the one 

 tendency (to seek black), while half followed the other 

 (to seek the side turned towards the light). 



Effect of various backgrounds and screens upon the 

 colour of the pup(e. 



It will not be necessary to provide such a detailed 

 analysis of the Experiments already described as in the 

 case of V. urticce, where the number of individuals was 

 much larger and the effect of crowding therefore greater, 

 nor shall I discriminate between the effects of the dif- 

 ferent kinds of gilt paper employed. But all necessary 

 data are supplied in the account of the Experiments 

 themselves, so that a more detailed analysis can be made 

 at any time. In order to economize space, the com- 

 parison of the effects of the various conditions will be 

 given in a tabular form, proceeding from the considera- 

 tion of darkness, black, brown, white, and colourless 

 surfaces to metallic backgrounds, and from these passing 

 to the colours of the spectrum from red to blue. Per- 

 centages will not be calculated for very small numbers 

 and single Experiments. 



