THE CAUSE OF MIMETIC EESEMBLANCE ETC. 507 



according as it resembled the object in question ; just as a similar 

 selection has been supposed to take place from the stimulus 

 supplied by the appearance of another species. Probably no one 

 is prepared to adopt this view as regards the former class of 

 facts, although Darwin had, as the above-quoted letter shows, 

 considered the possibility of the general tints of the environment 

 influencing the trend of sexual selection in this way. 



A fatal objection to any explanation based on the theory of 

 sexual selection is the fact that protective resemblances are so 

 extremely common and perfect in the immature stages of 

 insects. The same objection holds, although with less force, 

 against its use as an explanation of mimetic resemblance. 



The conclusion appears inevitable that under no theory except 

 natural selection do the various resemblances of animals for their 

 organic and inorganic environments fall together into a natural 

 arrangement and receive a common explanation. On any theory 

 except natural selection this c-m only be brought about by the 

 adoption of extreme views as to the area over which the alternative 

 theory is to be applied, — views which, at any rate, the great 

 majority of those who are disposed thus to explain mimetic 

 resemblance are not prepared to adopt. 



(4) Mimetic 'Resemblance and Common Warning Colours hetween 

 different Ai'tliropod Classes and betiveen va7'ioiis Insect Orders, 

 and their Relation to Similar Resemhhuices loitliin the Limits 

 of a Single Order. 



The discussion at the Entomological Society was based almost 

 exclusively upon the phenomena presented by mimetic resemblance 

 and common warning colours affecting the species of a single 

 Order of insects (Lepidoptera), and generally the species of a 

 single Family {Nymphalidce). I cannot but think that this 

 limitation of the survey to one small part of the field over which 

 the resemblances commonly occur is, in large part, the cause of 

 the rejection of natural selection aiid the substitution of alter- 

 native suggestions. There is something attractive and plausible 

 in the suggestion that the strong mutual resemblances within a 

 group of butterflies of different genera and subfamilies, inhabiting 

 a single locality, are due to the direct action of peculiar local 

 physical or chemical influences ; but the suggestion loses all its 

 attractiveness when it is ap[)lied to the resemblance between a 



