Chap. VII. CORRELATION OF GEOWTH. 2S9 



inner processes of the nasal bones ; and likewise the shape of 

 the external orifice of the nostrils. There is a plain and 

 curious correlation between a crest of feathers and the im- 

 perfectly ossified condition of the skull. Not only does this 

 hold, good with nearly all crested fowls, but likewise with 

 tufted ducks, and as Dr. Giinther informs me with tufted 

 geese in Germany. 



Lastly, the feathers composing the crest in male Polish 

 fowls resemble hackles, and differ greatly in shape from those 

 in the crest of the female. The neck, wing-coverts, and loins 

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

 would appear that feathers of this shape have spread by 

 correlation to the head of the male. This little fact is in- 

 teresting ; because, though both sexes of some wild gallina- 

 ceous 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. It would 

 therefore appear that the same law has regulated the state of 

 the feathers on the head and body, both with species living 

 under natural conditions, and with birds which have varied 

 under domestication. 



