Reply to Mr Wallace's Theory of Birds' Nests 141 



culated to draw forth much opposition. The failure lies in the 

 attempt to refer to blind chance (the chance of the production of 

 an accidental combination of design or an element which, by con- 

 tinued selection, shall ultimately assume the form of combined 

 design) structures which all — Darwinites not less than their 

 neighbours — admit to be examples of skilful and elaborate con- 

 trivance. 



But formidable as the objection is when stated merely to the 

 production of species, or instances of design in species, it becomes 

 infinitely more so when we are asked to extend its application to 

 sexual differences and periodical changes. See what Mr Wallace's 

 theory of birds' nests requires. Take his explanation of the 

 origination of dull-coloured female mates to bright-coloured male 

 birds. He starts with the assumption that originally both male and 

 female had bright plumage. There seems no reason why he should 

 begin with the assumption that they were both bright rather than 

 both dull-coloured ; but his argument is only directed to that side of 

 the question, and it would obviously have required a different line 

 of reasoning to convert a dull male into a bright male from that 

 which would convert a bright female into a dull female. In the 

 case of both being originally bright-coloured, there is a quasi 

 necessity for the female to become dull-coloured. There is the 

 supposed compulsion of the struggle for life. But in the case of 

 both being dull at first, that compulsion would not apply to the 

 male bird. There is no controuling necessity for him to put on 

 a finer coat than he had before. However, pass that, and let 

 us accept the question from the side which Mr Wallace pre- 

 sents to us — both male and female bright ; female sitting on 

 an open nest ; species like to be extinguished from the exposure ; 

 all enemies at once see her, and seize upon the eggs ; ruin stares 

 the species in the face. It has two modes of escape : one, an 

 easy and natural one, no ways beyond the instinct of a species 

 or the intellect of an individual, by building the nest in a more 

 concealed position ; the other, a more difficult one, wholly be- 

 yond its own control, the female becoming converted, by 

 Darwinian process of natural selection, from a bright-coloured bird 

 into a dull-coloured bird. According to Mr Wallace, some adopted 

 the easy remedy ; others did not, and in them a change in the 

 colour of the plumage was effected by natural selection. All the 

 females of the same species were, of course, not equally bright in 

 plumage \ and as the least brilliant females escaped observation 



