Correlation 
radiating from the sand on which these creatures 
dwell. 
White quills do not wear well either in 
domestic birds or in wild albinos. This may 
explain why it is that when a white wild species 
of bird has any black in its plumage the black is 
almost invariably on the tips of the wings. 
White quill-feathers are one of the commonest 
variations observed in domesticated birds, never- 
theless they are as rare as complete whiteness 
-among birds in their natural state. 
A chestnut or bay colour in mammals appears 
to be correlated with a high rate of speed, as in 
the thoroughbred horse. This perhaps explains 
why so many of the swiftest species of antelope, 
such as the hartebeests and sassaby (Damatliscus 
Zunatus), are chestnut bay in colour. It is further 
a remarkable fact that in the Black-buck (Axézlope 
ceruiucapra) and the Nilgai (Boselaphus trago- 
camelus) the females, which are faster than the 
males, are not black or grey like their respective 
males, but reddish. 
Wild turkeys are bronze; tame ones are black 
more often than any other colour. This may be 
due to the fact that in them nigritude is cor- 
related with the power to resist damp. Among 
human beings those races which live in very 
swampy districts are often intensely black. 
It is a significant fact that those domestic 
animals which are bred for speed or for fighting 
363 
