42 THE ZOOLOGIST. 
and upper wing-coverts are white, with dark shafts, dark centres, 
and dark margins. The central portion of the back presents a 
much blacker appearance, in consequence of each feather being 
dark, with a white margin; while the upper tail-coverts are 
marked like the scapulars, but darker in tone. The primaries 
and secondaries are grey, inclining to white at the extremities ; 
the tail-feathers white, broadly terminated with black, the white 
portion just above the black tips being somewhat speckled on 
both webs ; the under tail-coverts, as usual, pure white. 
Mr. Howard Saunders has remarked (Yarrell’s ‘ British Birds,’ 
* Ath ed., vol. ii., p. 67) that ‘‘ Examples of both sexes are some- 
times found with an unusual amount of white about their 
plumage, and this is especially the case with females from 
northern and north-eastern localities. Males from Siberia show 
more white than western specimens, but beautiful examples with 
white-mottled breasts and wing-coverts may also, though rarely, 
be obtained in Scotland.” Iam inclined to think that the ‘‘ white- 
mottled breast’ denotes immaturity, as it does in the case of the 
Cormorant, and therefore cannot be regarded as abnormal. 
We have yet, however, a good deal to learn on the subject of 
variation, and the causes which tend to produce it. Darwin has 
expressed the opinion that “‘ Variability of every kind is directly 
or indirectly caused by changed conditions of life”’ (op. cit., vol. ii., 
p. 255), and considered it ‘‘doubtful whether a change in the 
nature of the food is a potent cause of variability” (p. 257); for 
as he truly observes, ‘‘Searcely any domesticated animal has 
varied more than the pigeon, or the fowl, yet their food, especially 
that of highly-bred pigeons, is generally the same.” 
It will be seen that these remarks apply chiefly to animals 
under domestication, for, in a state of nature, individuals of 
the same species are exposed to nearly uniform conditions, 
being rigorously kept to their proper places by a host of com- 
petitors, and have moreover long been habituated to their 
conditions of life. At the same time it cannot be said that they 
are subject to quite uniform conditions, and they are liable to a 
certain amount of variation. In the case of game-birds, doubtless 
those which, like the Pheasant, are brought more directly under 
the influence of man are more. liable to variation. The Black 
Grouse which, except by hybridisation, varies very little, is only 
to be found in wild haunts far removed from human habitation. 
