128 THE VALUE OF COLOUR 



abundant conspicuous butterflies which he saw 

 exhibiting mimetic hkenesses. The common 

 instances in his locahty, and indeed everywhere 

 in tropical America, were anything but the hard- 

 pressed struggling forms assumed by the theory 

 of Bates. They belonged to the groups which 

 were themselves mimicked by other butterflies. 

 Fritz MtlUer's suggestion also shows that he did 

 not accept Bates's alternative explanation of a 

 superficial likeness between models themselves, 

 based on some unknown influence of local physico- 

 chemical forces. At the same time MtiUer's own 

 suggestion was subject to this apparently fatal 

 objection, that the Sexual Selection he invoked 

 would tend to produce resemblances in the males 

 rather than the females, while it is well known 

 that when the sexes differ the females are almost 

 invariably more perfectly mimetic than the males 

 and in a high proportion of cases are mimetic 

 whUe the males are non-mimetic. 



The difficulty was met several years later by 

 Fritz Miiller's well-known theory, published in 

 1879,^ and immediately translated by Meldola 

 and brought before the Entomological Society. ^ 

 Darwin's letter to Meldola dated June 6, 1879, 

 shows ' that the first introduction of this new and 

 most suggestive hypothesis into this country was 

 due to the direct influence of Darwin himself, 

 who brought it before the notice of the one man 

 who was likely to appreciate it at its true value 



' Kosmos, May, 1879, 100. ' Proc. Ent. Soc. Lond., 1879, xx. 



