220 THE COLOURS OF ANIMALS 



another respect. It not only supported the doctrine of 

 evolution, but it afforded strong confirmation of the 

 theory of natural selection, by which Darwin explained 

 how it was that evolution took place. Every step in 

 the gradually increasing change of the mimicking in 

 the direction of specially protected form, would have 

 been an advantage in the struggle for existence, while 

 the elements out of which the resemblance was built 

 exist in the individual variability of the species, a 

 variability which is hereditary. 



The transition from Warning to Mimetic appearances 



It will have been observed that Mimicry has already 

 been mentioned in the pages on Warning Colours, and 

 that a gradual transition may be traced from the one 

 principle to the other. And yet Mimicry itself was 

 explained long before many of the conclusions con- 

 cerning Warning Colours which have been described. 

 In this, as in so many other cases, the steps by which 

 the subject is best approached are almost exactly oppo- 

 site to the historical steps by which it was gradually 

 understood. 



The transition from warning to mimetic forms 

 may be shortly recapitulated. 



1. The existence of Warning colours, attitudes, &c. 

 in species which possess some quality unpleasant to the 

 enemies of their class : recognised by Bates in butter- 

 flies which are mimicked by others (loc. cit. 1862) ; the 



