54 MIMICRY AND HOMOPLASY 



be mistaken for it, although the two may not 

 be really allied and often belong to distinct 

 families or orders." The first constant condition 

 under which true mimicry occurs is "that the 

 imitative species occur in the same area and 

 occupy the very same station as the imitated." 

 The last essential condition of mimicry, as 

 explained by Mr Wallace, is "that the imita- 

 tion, however % minute, is external and visible 

 only, never extending to internal characters or 

 to such as do not affect the external appearance." 

 Furthermore, it is explained that warning colora- 

 tion is the basis of the phenomenon of mimicry, 

 but it is not stated what lies at the root of 

 warning coloration. Of course it is fostered by 

 natural selection, but we do not know the funda- 

 mental reaction that determines it. Professor 

 Poulton l adds as another attribute of true 

 mimicry that it is a sham, that is to say, a 

 false alarm ; true warning colours, occurring in 

 unpalatable or dangerous bodies, are genuine. 



Warning coloration, mimicry, protective re- 

 semblance, and the death feint, are facts in 

 nature which are known to have been doubted 

 in the past by "armchair philosophers." This 

 has doubtless been due to the fact that some 

 delicate shade of meaning has often been over- 

 looked in the original descriptions. Even if 



1 E. B. Poulton, " Colours of Animals," Encyc. Brit., ninth 

 edition, Supplement. 



