274 
Proceedings of the Royal Society 
the view of indicating the relative size of male and female, of 
pointing out the profuse and almost grotesque ornamentation of 
the males at the breeding season, and of showing the wide variation 
in the plumage of male birds especially. During the breeding 
season numerous papillaa, or fleshy tubercules, appear on the face, 
a couple of ear tufts slope gracefully to the hind head, and a large 
frill or ruff of elongated feathers surrounds the neck. These fea- 
tures continue till about the middle of June, when the birds moult. 
They then put on the autumn and winter garb. It is next to im- 
possible to find two males ornamented alike. But it is known that 
the colouring of the frill first assumed is retained through all the 
changes of plumage that follow in after years. If red originally, 
it will have that colour as successive breeding times come round. 
If black, or white, these colours reappear in their season. The 
fact is curious and interesting from the physiological point of view. 
The theory of sexual selection does not help to explain it. The 
birds are polygamous, and the male has to fight to obtain the 
female. It is not, however, the size or colour of the frill, but the 
strength of beak and of leg that conquers. Then what is it that 
determines the colour of the frill in different birds of the same 
species, and what keeps the hue persistent throughout all the yearly 
changes of plumage? The questions are easily put. One would 
like if they were as easily answered. 
