Holmes, The Reactions of Ranatra to Light. 349 



mechanical procedure as the phototaxis of Ranatra we encoun- 

 ter peculiarities which indicate that we have not struck bottom 

 in our analysis of the phenomenon. 



In many ways the phototaxis of the Ranatra seems to be 

 intermediate between purely reflex conduct on the one hand 

 and conduct of the pleasure-pain type on the other. These two 

 kinds of behavior seem to be harmoniously combined in many 

 instincts, if not in most of the more highly involved modes of 

 instinctive action. Just what the steps are which lead from the 

 one to the other we do not know. We are still in want of a 

 satisfactory explanation of the pleasure-pain type of response. 

 When we are able to supply one we shall be in a position to 

 give a more adequate interpretation of the phototaxis of higher 

 forms than can be supplied at the present time. 



