lo The Descent of Man 



succeeds in obtaining possession of mates and in keeping 

 away rivals. This is, undoubtedly, a vera causa ; but may 

 be more conveniently reckoned as one kind of ' natural selec- 

 tion' than as a branch of 'sexual selection.' The second 

 process consists in alleged preference or choice, exercised 

 freely by the female, in favour of particular males on account 

 of some attractiveness or beauty of form, colour, odour, or 

 voice, which such males may possess. It is this second kind 

 of ' sexual selection ' (and which alone deserves the name) 

 that is important for the establishment of Mr Darwin's views, 

 but the efficiency of its action has to be proved. 



Now, to prove the existence of such a power of choice Mr. 

 Darwin brings forward a multitude of details respecting the 

 sexual phenomena of animals of various classes ; but it is the 

 class of birds which is mainly rehed on to afford evidence in 

 support of the exercise of this power of choice by female 

 animals. We contend, however, that not only is the evidence 

 defective even here, ^but that much of his own evidence is 

 in direct opposition to his views. While the unquestionable 

 fact, that male sexual characters (horns, mane, wattles, etc., 

 etc.) have been developed in many cases where sexual selec- 

 tion has certainly not acted, renders it probable, d priori, 

 that the unknown cause which has operated in these 

 numerous cases has operated in those instances also which 

 seem to favour the hypothesis supported by Mr. Darwin. 

 Still he contends that the greater part of the beauty and 

 melody of the organic world is due exclusively to this selec- 

 tive process, by which, through countless generations, the 

 tail of the peacock, the throat of the humming-bird, the song 

 of the nightingale, and the chirp of the grasshopper have 

 been developed by females, age after age, selecting for their 

 mates males possessing in a more and more perfect degree 

 characters which must thus have been continually and con- 

 stantly preferred. 



