210 TROPICAL NATURE, AND OTHER ESSAYS. 



complete adaption to conditions, tliat the inconvenience 

 or danger produced by such ornaments was so com- 

 paratively small as not to affect the superiority of the 

 race over its nearest allies. 



But if those portions of the plumage, which were 

 originally erected under the influence of anger or fear, 

 became largely developed and brightly coloured, the 

 actual display, under the influence of jealousy or sexual 

 excitement becomes quite intelligible. The males, in 

 their rivalry with each other, would see what plumes 

 were most effective ; and each would endeavour to excel 

 his enemy as far as voluntary exertion would enable him^ 

 just as they endeavour to rival each other in song, even 

 sometimes to the point of causing their own destruction. 



Natural Selection as Neutralizing Sexual Selection. 

 — There is also a general argument against Mr. Darwin's 

 views on this question, founded on the nature and 

 potency of " natural " as opposed to " sexual " selection, 

 which appears to me to be of itself almost conclusive 

 as to the whole matter at issue. Natural selection, or 

 the survival of the fittest, acts perpetually and on an 

 enormous scale. Taking the offspring of each pair of 

 birds as, on the average, only six annually, one-third 

 of these at most will be preserved, while the two-thirds 

 which are least fitted will die. At intervals of a few 

 years, whenever unfavourable conditions occur, five- 

 sixths, nine-tenths, or even a greater proportion of the 

 whole yearly production are weeded out, leaving only 

 the most perfect and best adapted to survive. Now 

 unless these survivors are, on the whole, the most 

 ornamental, this rigid natural selection must neutralise 

 and destroy any influence that may be exerted by 



