No. 605] 



ANIMAL COLORATION 



the reader may judge whether a passage between Scylla 

 and Charybdis may be made in safety. 



Professor Poulton's extensive studies have convinced 

 him that the evolution of mimetic resemblance has been 

 directed by natural selectionj^*^ yet the evidence upon 

 which his conclusion rests may be taken over bodily and 

 supports the* revised hypothesis as consistently as that 

 to whose service it was originally dedicated. There is 

 nothing anomalous in finding mimic and model living 

 under the same conditions, certain groups of insects show- 

 ing the same series of local color varieties, or such diver- 

 sity of coloration appearing in one group of butterflies 

 or moths as allies them outwardly with different "pro- 

 tected" genera. The same is true of the fact that insects 

 with every variety of larval experience as adults possess 

 the same type of coloration, that mimetic females are 

 more common than males, or that the common coloration 

 possessed by mimic and model is attained in the most 

 diverse fashion, that is, that cases of mimicry are typical 

 instances of analogy. Throughout the whole series of 

 observations the points of agreement and difference are 

 consistent, as far a> is ktiowii. with the fundamental as- 

 sumption that color ;iti(l liabit art' associated variables. 



Passing to the negatixc side of the argument, we may 

 first consider the statement that it is impossible that re- 

 ciprocal mimicry should have been brought about by 

 natural selection of small variations. Punuett has this 

 idea from MarshalP^ and uses it to emphasize the diffi- 

 culty of the initial variation even in cases where it might 

 seem that the theoretical advantage to be gained from 

 mutual resemblance h\ two -jxu'ie^ ^\ould simplify the 

 attainment of likeness. I'.nt Dixcv,'- against whose posi- 

 tion the argument wa- oiunialK iliiccted, ha^ exposed it- 

 unsoundness by calliii-:- arttMitidii to a number of critical 



