on MiiUerian Mimicry and Biaposematism. 561 



The variation simply fits iato a new place, leaving its 

 ancestral stock to keep on in the old one. 



Mr. Marshall goes on to point out (p. 96) that "the 

 mental attitude of the enemy towards its prey has an im- 

 portant bearing upon the results which its attacks will 

 produce." Upon this statement, which is no doubt true 

 enough, he bases the conclusion that " those enemies which 

 have a comparatively low degree of intelligence, and which 

 therefore require to make many experiments ..." operate 

 more efficiently as producers of MiiUerian mimicry than 

 those enemies whose superior intelligence enables them 

 to " profit more quickly by their experience." But, he 

 goes on to say, " if there be enemies still lower in the 

 scale and incapable of forming such a mental association 

 [between colour and inedibility] at all, then the destruction 

 of butterflies which they would cause would have no effect 

 whatever from a purely mimetic standpoint." It would be 

 interesting to know whether Mr. Marshall is prepared to 

 indicate the exact point in the descending scale of intelli- 

 gence at which will occur the transition from the greatest 

 efficiency in the production of MiiUerian mimicry to no 

 efficiency at all. Moreover, although the more intelligent 

 enemy will doubtless learn its lesson more quickly, it may 

 also, as Mr. Marshall points out in the next paragraph, 

 discriminate more readily and therefore experiment more 

 freely, the two tendencies acting to some extent in opposite 

 directions. 



With regard to Batesian mimicry, it does not seem al- 

 together clear that superior intelligence operates quite as 

 Mr. Marshall thinks it does. It may, on the one hand, as 

 he says, enable the enemy to discriminate between mimic 

 and model ; but, on the other, it may also assist its possessor 

 to recognise a warning sign which would be passed un- 

 noticed by an enemy of lower mental equipment. It would 

 not be easy to say for certain whether a close mimetic 

 resemblance is an appeal to superior cleverness or superior 

 stupidity. For such reasons as these I feel doubtful as to 

 the validity of Mr. Marshall's expectation " that the elimin- 

 ation due to the Batesian factor would be competent to 

 produce a higher degree of inter-resemblance than would 

 the factor adduced by Fritz Miiller." 



In his next paragraph Mr. Marshall deals with a possible 

 difference in the periods of incidence of the two mimetic 

 processes. I am not sure that his account of the effect of 



