SEXUAL SELECTION 215 



selection ' of Darwin is an important factor in the transformation of 

 species, even if I only take into consideration those secondary sexual 

 characters which are related to wooing. We shall see, however, that 

 there are others in regard to whose origin through processes of 

 selection doubt is still less legitimate, and from which, on this 

 account, we can argue back to the courtship characters. 



The first beginning of transformation is not, even in ordinary 

 natural selection, to be understood as due to selection, but is to be 

 regarded as a given variation (the causes of which we shall discuss 

 later on) ; it is only the increase of such incipient variations in 

 a definite direction that can depend on natural selection, and they 

 must depend on it in so far as the transformations are purposeful. 

 Now, all secondary sexual characters can be recognized as useful, 

 save only the decorative distinctions, although these also undoubtedly 

 represent intensifications of originally unimportant variations. Are 

 we then to reo-ard these alone as the mere outcome of the internal 

 impulsive forces of the organism, while in the case of the analogous 

 sexual characters for tracking, catching, and holding the female, and 

 so forth, the augmentation and the directing must be referred to 

 processes of selection 1 But if there be any utility at all in the 

 decorative sexual characters it can only lie in their greater attrac- 

 tiveness to the females, and it can only be of any account if the 

 females have, in a certain sense, the power of choice. Independently, 

 therefore, of direct observations as to the actual occurrence of choos- 

 ing, we should be compelled by our chain of reasoning to assume that 

 there was such a power of choice — and I shall immediately discuss it 

 more precisely. 



If we consider the decorative, distinctive characters of the males 

 more closel}^ we find that they are of very diverse kinds. The males 

 of many animals are distinguished from the females chiefly by greater 

 beauty of form, and especially of colour. This is the case in many 

 birds, some amphibians, like the water-salamander, many fishes, many 

 insects, and above all, in diurnal Lepidoptera. Especially among birds 

 the dimorphism between the sexes is in obvious relation to the excess 

 in the number of male individuals, or — what practically comes to the 

 same thing— to polygamy. For when a male attaches to himself four 

 or ten females the result is the same as if the number of female 

 individuals were divided by four or by ten. Thus the fowls and 

 pheasants, which are polygamous, are adorned by magnificent colours 

 in the male sex, while the monogamous partridges and quails exhibit 

 the same colourino; in both sexes. Of course ' beautiful ' is a relative 

 term, and we must not simply assume that what seems beautiful to 



