Chaf. VII. CORRELATION OF GKOWTH. 275 



in the male bird are properly covered with hackles, and it 

 would appear that feathers of this shape have spread by corre- 

 lation to the head of the male. This little fact is interesting ■ 

 because, though both sexes of some wild gallinaceous birds 

 have their heads similarly ornamented, yet there is often a 

 difference in the size and shape of feathers forming their 

 crests. Furthermore there is in some cases, as in the male Gold 

 and in the male Amherst pheasants (P. pictus and Amherstice), 

 a close relation in colour, as well as in structure, between the 

 plumes on the head and on the loins. Hence it would appear 

 that the same law has regulated the state of the feathers 

 on the head and body, both with species living under their 

 natural conditions, and with birds which have "varied under 

 domestication. 



t 2 



