Mimetic Attraction. 327 



it will be sufficient to point out that there is more reason 

 to suppose that the Heliconius has adopted certain 

 features from the Pieris (for example, the whiteness of 

 the ground colour, and the disposition, if not the exist- 

 ence, of the basal red marks) than that the converse 

 alone has taken place. 



Reciprocal Mimicry and Convergence. This fact of the 

 reciprocal copying of two or more species by each 

 other is perhaps implied, though not distinctly so, 

 in the term "convergence," which has been used 

 by many authors to express the phenomenon of Miil- 

 lerian mimicry; but I am not aware that any writer 

 who so employs the term has laid stress on the mutual 

 character of the changes involved, or has traced ui 

 any instance the actual modifications undergone by 

 both species of a Miillerian couple under the intluence 

 of the attractive force existing between them. It seems 

 hitherto to have been taken for granted that a dominant 

 form will attract or retain other species within its own 

 sphere of influence, without being itself attracted in 

 return ; whereas the fact is, as we have seen, that each 

 member of an inedible association has more or less 

 influence upon all the rest. The respective value of the 

 attraction exercised or sufl"ered by any member of a 

 Miillerian group will depend on its numbers, its nauseous 

 qualities, and its notoriety. The stronger any species is 

 in these respects, the stronger will be its power of 

 attraction, and the weaker in comparison will be any 

 force tending to draw it in the direction of other mem- 

 bers of the group. The actual mimetic path taken by 

 any species will be the resultant of the various forces 

 acting upon it. If the form happens to be a dominant one, 

 these external forces will be insignificant in comparison 

 with its own stability -, and it will therefore resist change 

 to a large extent, or perhaps altogether. The most com- 

 plete intermingling of characters given and taken on 

 both sides may be expected when two species meet on 

 equal terms, neither being strong enough to predominate 

 over the other. 



While there can be no doubt of the convenience of the 

 term "convergence,'' and its suitability to express 

 relations of the kind just discussed, there would seem to 

 be no suflicient reason for disallowing in their case the 

 earlier term " mimicry.'' This latter word may be quite 



