1 2 The Field Naturalist's Quarterly Feb. 



the arctic regions display at the beginning of winter, is a 

 phenomenon sui generis, and without even parallel. Never- 

 theless, it cannot be too strongly insisted upon that this 

 assumption of a white pelage, or of white feathers, is merely 

 an extreme case of a change which is general, and indeed 

 nearly universal, among mammals and birds. Quite apart 

 from the putting on of a thicker coat in winter, as exempli- 

 fied by the Camel, the Bison, and other animals which are 

 dwellers in temperate climates, there is frequently a distinct 

 change of colour at that season, which is not necessarily a 

 change to white. The change may, in fact, be in the direc- 

 tion of a darker hue : the Snow Bunting, for instance, has 

 not so much white among its feathers in the winter as in 

 the summer. Generally, however, the paler hues — if there 

 is a difference of the kind between winter and summer coat — 

 are peculiar to the winter. Thus the Reindeer is paler in the 

 colder season than in the summer; the Grey Phalarope in 

 summer is tinged with various shades of brown, while in the 

 winter it is white and grey and quite gull-like in hue, a fact 

 which is incidentally of some importance in considering the 

 very near relationship which the Limicoline birds most un- 

 questionably bear to the Gulls. Mr Keeler, the author of 

 an important treatise upon the colours of American birds, 

 which contains many reflections of value upon the general 

 problems to which the facts which he has industriously 

 collected give rise, points out that the American Dipper 

 (Cinclns mexicanus) has a white breast in winter. 



The extreme, then, of these seasonal changes in colour 

 are to be seen in certain denizens of the polar regions, and 

 even of the more temperate countries bordering upon these, 

 where there is not only a paling of the summer hues in 

 winter, but an actual change to a snow - white plan of 

 colouration which differs from albinism, superficially at any 

 rate, in the fact that the pigment is not entirely lost, but is 

 retained in various parts of the body, such as the snout and 

 eyes in the " White Fox," and the tip of the tail in the Stoat 

 or Ermine. Furthermore, the winter pelage is sometimes 

 remote from albinism in other ways. It is probable that 

 the white colour of the hairs is not always real ; it is at 

 least sometimes apparent, and due to masking of pigment 



