OH. xxxviii.] CHANGES OF PLUMAGE. 399 



after these clianges are fully completed that the red side 

 plumes begin to appear. 



The successive stages of development of the colours and 

 plumage of the Birds of Paradise are very interesting, from 

 the striking manner in which they accord with the theory 

 of their having been produced by the simple action of 

 variation, and the cumulative power of selection by the 

 females, of those male birds which were more than usually 

 ornamental. Variations of colour are of all others the 

 most frequent and the most striking, and are most easily 

 modified and accumulated by man's selection of them. 

 We should expect, therefore, that the sexual differences of 

 colour would be those most early accumulated and fixed, 

 and would therefore appear soonest in the young birds; 

 and this is exactly what occurs in the Paradise Birds. Of 

 all variations in the form of birds' feathers, none are so 

 frequent as those in the head and tail. These occur more 

 or less in every family of birds, and are easily produced in 

 many domesticated varieties, while unusual developments 

 of the feathers of the body are rare in the whole class of 

 birds, and have seldom or never occurred in domesticated 

 species. In accordance with these facts, we find the scale- 

 formed plumes of the throat, the crests of the head, and 

 the long cirrhi of the tail, all fully developed before the 

 plumes which spring from the side of the body begin to 

 make their appearance. If, on the other hand, the male 



