64 "MIMICRY RINGS" [ch. 



modified through any agency, the imitating form would be led 

 along the same track, and thus be altered to almost any extent, so 

 that it might ultimately assume an appearance or colouring wholly 

 unlike that of the other members of the family to which it belonged. 

 There is, however, some difficulty on this head, for it is necessary 

 to suppose in some cases that ancient members belonging to several 

 distinct groups, before they had diverged to their present extent, 

 accidentally resembled a member of another and protected group 

 in a sufficient degree to afford some slight protection; this having 

 given the basis for the subsequent acquisition of the most perfect 

 resemblance^. 



Both Darwin and Wallace recognised clearly this 

 difficulty of the initial variations, and both suggested 

 a means of getting over it on similar lines. Both 

 supposed that in general colour and pattern the groups 

 to which model and mimic belonged were far more 

 alike originally than they are to-day. They were 

 in fact so much ahke that comparatively small varia- 

 tions in a favourable direction on the part of the mimic 

 would lead to its being confused with the unpalatable 

 model. Then as the model became more and more 

 conspicuously coloured, as it developed a more and 

 more striking pattern warning would-be enemies of 

 its unpleasant taste, the mimic gradually kept pace 

 with it through the operation of natural selection, 

 in the shape of the discriminating enemy, eliminating 

 those most unlike the model. The mimic travelled closely 

 in the wake of the model, coaxed as it were by natural 

 selection, tiU at last it was far removed in general 

 appearance from the great majority of its near relations. 



1 Origin of Species, 6th Edition, 1891, p. 354. 



