OTHER THEORIES OF SEXUAL COLOURING 319 



The musical value of the song of birds cannot be explained 

 as a means of Recognition between the sexes 



Similar objections may be urged against Mr. 

 Wallace's contention that the songs of birds are to 

 be explained as a means of recognition, and that their 

 * production, intensification, and differentiation are 

 clearly within the power of natural selection.' Eecog- 

 nition between the sexes, and invitation from the male 

 to the female, are most important benefits conferred 

 by song, but these can never account for the marvel- 

 lous degree of elaboration, and the high musical value 

 of the results attained by many of our singing birds. 

 The beauty of song is something more than its ' clear- 

 ness, loudness, and individuality,' just as the beauty 

 of appearance is something more than its conspicuous- 

 ness ; and the fact that these two forms of beauty are 

 complementary, so that the brightest birds do not sing, 

 while song birds are sober in appearance, is quite 

 consistent with the origin of these qualities by the 

 accumulated results of female preference. We know 

 that the excessive cultivation of one taste is inconsis- 

 tent with the equal cultivation of others, and when 

 the small brain of a bird is constantly directed to 

 appreciating the beauty of song, it may well become 

 comparatively indifferent to beauty of person. Be- 

 sides, the qualities conferred by this means are always 

 more or less of a danger to the species, and an especi- 



