ANIMALS THAT CHANGE COLOUR 75 
the creature is changing its summer for its 
winter coat, the new fur appears of the same 
colour as that previously worn, and does not 
alter until the colder weather sets in. On 
the other hand, if the weather is cold when 
the winter pelage commences to grow its 
colour is white at the outset. 
The arctic-fox and the mountain-hare are 
other creatures which wear different-coloured 
liveries during the summer and winter months. 
A large number of the feathered folk assume 
different hues after their periodic moults, but 
it is not always that the change of colour is 
due entirely to the production of new feathers, 
for in the ptarmigan, a bird which indulges 
in the practice of wearing a different suit 
during the summer, autumn and winter months, 
the pigments of the feathers undergo a trans¬ 
formation of tint. 
Abnormal colour changes may sometimes 
occur in animals, which in some cases may 
be due to selective breeding, and in others 
to some 4 4 sport ” of Nature. The writer has 
seen a green tree-frog which, to use a some¬ 
what 44 Irish ” expression, was of a bright 
blue tint; while yellow, as well as sky-blue, 
varieties of the familiar and normally green- 
coloured budgerigars or love-birds have been 
successfully reared and established as distinct 
