6 Colouration in Animals and Plants. 



brilliant males, and that by continued selection of this character, 

 the sexual hues have been gradually evolved. 



To this theory Wallace takes exception. Admitting, as all 

 must, the fact of sexually distinct ornamentation, he demurs to the 

 conclusion that they have been produced by sexual selection. 



In the first place, he insists upon the absence of all proof 

 that the least attractive males fail to obtain partners, without 

 which the theory must fail. Next he tells us that it was the case 

 of the Argus pheasant, so admirably worked out by Darwin, that 

 first shook his faith in sexual selection. Is it possible, he asks, 

 that those exquisite eye-spots, shaded " like balls lying loose 

 within sockets " (objects of Avhich the birds could have had no 

 possible experience) should have been produced ..." through 

 thousands and tens of thousands of female birds, all preferring 

 those males whose markings varied slightly in this one direction, 

 this uniformity of choice continuing through thousands and tens 

 of thousands of generations " '? * 



As an alternative explanation, he would advance no new theory, 

 but simply apply the known laws of evolution. He points out, and 

 dwells upon, the high importance of protection to the female while 

 sitting on the nest. In this way he accounts for the more sombre 

 hues of the female ; and finds strong support in the fact that in 

 those birds in which the male undertakes the household duties, he 

 is of a domestic dun colour, and his gad-about-spouse is bedizened 

 like a country-girl at fair time. 



With regard to the brilliant hues themselves, he draws attention 

 to the fact that depth and intensity of colour are a sign of vigour 

 and health — that the pairing time is one of intense excitement, and 

 that we should naturally expect to find the brightest hues then 

 displayed. Moreover, he shows — and this is most important to us — 

 that " the most highly-coloured and most richly varied markings 

 occur on those parts which have undergone the greatest modifi- 

 cation, or have acquired the most abnormal development." t 



It is not our object to discuss these rival views ; but they are 

 here laid down in skeleton, that the nature of the problem of the 

 principles of colouration may be easily understood. 



Seeing, then, how infinitely varied is colouration, and how 

 potently selection has modified it, the question may be asked, " Is 



* Wallace, Tropical Nature, p. 20(3. f Op. cit., p. 206. 



