322 The Descent of Man. Pakt li. 



inheritance by both sexes has prevailed, the selectioii of bright- 

 coloured males would tgnd to make the females bright-coloured; 

 and the selection of dull-coloured females would tend to make 

 the males dull. If both processes were carried on simultaneously, 

 they would tend to counteract each other ; and the final result 

 would depend on whether a greater number of females from 

 being well protected by obscure colours, or a greater number of 

 males by being brightly-coloured and thus finding partners, 

 succeeded in leaving more numerous offspring. 



In order to account for the frequent transmission of characters 

 to one sex alone, Mr Wallace expresses his belief that the more 

 common form of equal inheritance by both sexes can be chan.^ed 

 through natural selection into inheritance by one sex alone, but 

 ill favour of this view I can discover no evidence. We know 

 from what occurs under domestication that new characters often 

 appear, which from the first are transmitted to one sex alone : 

 and by the selection of such variations there would not be the 

 slightest difficulty in giving bright colours to the males alone, 

 and at the same time or subsequently, dull colours to the females 

 alone. In this manner the females of some btitterflies and moths 

 have, it is probable, been rendered inconspicuous for the sake of 

 protection, and widely different from their males. 



I am, however, unwilling without distinct evidence to admit 

 that two complex processes of selection, each requiring the 

 transference of new characters to one sex alone, have been 

 carried on with a multitude of species, — that the males have 

 been rendered more brilliant by beating their rivals, and the 

 females more dull-coloured by having escaped from their 

 enemies. The male, for instance, of the common brimstone 

 butterfly (Gonepteryx), is of a far more intense yellow than the 

 female, though she is equally conspicuous; and it does not seem 

 probable that she specially acquired her pale tints as a protec- 

 tion, though it is probable that the male acquired his bright 

 colours as a sexual attraction. The female of Anthodiaris car- 

 damines does not possess the beautiful orange wing-tips of the 

 male; consequently she closely resembles the white butterflies 

 (Pieris) so common in our gardens ; but we have no evidence 

 that this resemblance is beneficial to her. As, on the other hand, 

 3he resembles both sexes of several other species of the genus 

 inhabiting various quarters of the world, it is probable that she 

 has simply retained to a large extent her primordial colours. 



Finally, as we have seen, various considerations lead to the 

 (lonolusioa that with the greater number of brilliantly-coloured 

 fjcpidoptera it is the male which has been chiefly modified 

 tlirongh sexual selection; the amount of difference betwiieu 



