BIRDS. 527 



I conclude, therefore, that the habit of moulting twice 

 in the year was in most or all cases first acquired for some 

 distinct purpose, perhaps for gaining a warmer winter cov- 

 ering; and that variations in the plumage occurred during 

 the summer were accumulated through sexual selection, 

 and transmitted to the offspring at the same season of the 

 year : that such variations were inherited either by both 

 sexes or by the males alone, according to the form of inher- 

 itance which prevailed. This appears more probable than 

 that the species in all cases originally tended to retain 

 their ornamental plumage during the winter, but were 

 saved from this through natural selection, resulting from 

 the inconvenience or danger thus caused. 



I have endeavored in this chapter to show that the argu- 

 ments are not trustworthy in favor of the view that weap- 

 ons, bright colors, and various ornaments are now confined 

 to the males owing to the conversion, by natural selection, 

 of the equal transmission of characters to both sexes, into 

 transmission to the male sex alone. It is also doubtful 

 whether the colors of many female birds are due to the 

 preservation, for the sake of protection, of variations 

 which were from the first limited in their transmission to 

 the female sex. But it will be convenient to defer any 

 further discussion on this subject until I treat, in the fol- 

 lowing chapter, of the differences in plumage between the 

 young and old. 



