414 SEXUAL SELECTION. Part II. 



they could not escape so swiftly from their enemies, 

 we can understand how they alone might originally 

 have acquired through natural selection and sexually- 

 limited inheritance their present protective colours. 

 But except on the principle of these variations having 

 been transmitted exclusively to the female offspring, 

 we cannot understand why the males should have re- 

 mained dull-coloured ; for it would surely not have 

 been in any way injurious to each individual male to 

 have partaken by inheritance of the protective colours 

 of the female, and thus to have had a better chance 

 of escaping destruction. In a group in which brilliant 

 colours are so common as with butterflies, it cannot be 

 supposed that the males have been kept dull-coloured 

 through sexual selection by the females rejecting the 

 individuals which w r ere rendered as beautiful as them- 

 selves. We may, therefore, conclude that in these cases 

 inheritance bv one sex is not due to the modification 

 through natural selection of a tendency to equal inherit- 

 ance by both sexes. 



It may be well here to give an analogous case in 

 another Order, of characters acquired only by the female, 

 though not in the least injurious, as far as we can judge, 

 to the male. Amongst the Phasinicke, or spectre-insects, 

 Mr. Wallace states that " it is often the females alone 

 " that so strikingly resemble leaves, while the males show 

 " only a rude approximation." Now, whatever may be 

 the habits of these insects, it is highly improbable that 

 it could be disadvantageous to the males to escape de- 

 tection by resembling leaves. 31 Hence we may conclude 



31 See Mr. Wallace in 'Westminster Keview,' July, 1867, p. 11 and 

 37. The male of no butterfly, as Mr. Wallace informs me, is known to 

 differ in colour, as a protection, from the female ; and he asks me how 

 I can explain this fact on the principle that one sex alone has varied 

 and has transmitted its variations exclusively to the same sex, without 



