Correlation 
may be due to a correlation with the power of 
withstanding intense dry heat rather than to its 
rendering them inconspicuous to their foes. 
As other examples of correlation we may cite 
the correlation which seems to obtain between 
short canine teeth and the absence of a hairy 
covering to the body. This phenomenon is 
observed both in men and pigs. Hairless dogs 
almost invariably have their teeth but poorly 
developed. 
Darwin called attention to the connection 
between a short beak and small feet in pigeons ; 
we see the same phenomenon in the dwarf breed 
of ducks known as call-ducks. 
A curious correlation exists between fowls’ 
eggs with brown shells and the incubating habit. 
Fanciers have long tried in vain to produce a 
hen that lays brown eggs without becoming 
‘‘broody” at certain seasons. 
Among fowls, long legs are invariably cor-. 
related with a short tail, as is well seen in the 
Malay breed. This correlation may explain the 
short tails of wading birds. Short-legged fowls, 
like Japanese bantams, have long tails, and it is 
significant that the short-legged Weka Rails 
(Ocydromus) of New Zealand have unusually 
long tails for the family. In this connection we 
may say that the tail-like plumes of the cranes 
are not tail-feathers, but the tertiary feathers of 
the wings. As egrets also have long trains of 
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