SEXUAL SELECTION 631 



trary being often eliminated as dangerous— while similar 

 variations occurring at or near the period of reproduction 

 have been preserved, it follows that the plumage of the 

 young will often have been left unmodified, or but little 

 modified. We thus get some insight into the coloring of 

 the progenitors of our existing species. In a vast number 

 of species, in five out of our six classes of cases, the adults 

 of one sex or of both are bright colored, at least during the 

 breeding season, while the young are invariably less brightly 

 colored than the adults, or are quite dull colored, for no in- 

 stance is known, as far as I can discover, of the young of 

 dull-colored species displaying bright colors, or of the young 

 of bright-colored species being more brilliant than their par- 

 ents. In the fourth class, however, in which the young and 

 the old resemble each other, there are many species (though 

 by no means all) of which the young are bright colored, and 

 as these form whole groups we may infer that their early 

 progenitors were likewise bright. With this exception, if 

 we look to the birds of the world, it appears that their 

 beauty has been much increased since that period of which 

 their immature plumage gives us a partial record. 



On the Color of the Plumage in relation to Protection. — It 

 will have been seen that I cannot follow Mr. Wallace in the 

 belief that dull colors, when confined to the females, have 

 been in most cases specially gained for the sake of protec- 

 tion. There can, however, be no doubt, as formerly re- 

 marked, that both sexes of many birds have had their 

 colors modified, so as to escape the notice of their ene- 

 mies; or in some instances, so as to approach their prey 

 unobserved, just as owls have had their plumage rendered 

 soft, that their flight may not be overheard. *Mr. Wallace 

 remarks" that "it is only in the tropics, among forests 

 which never lose their foliage, that we find whole groups 

 of birds, whose chief color is green. ' ' It will be admitted 



*• "Westminster Review," July, 1867, p. 5. 



