CLOTHING OF ANIMALS. 25 



of a wax-yellow ; and, lastly, of a yellowishrbrown. The 

 same process must be gone through in autumn, only rever- 

 sed, and with the addition of a suit of white. The absur- 

 dity of this supposition is too apparent to be farther ex- 

 posed. 



" With respect to the opinion which we have advanced, 

 it seems to be attended with few difficulties. We urge not 

 in support of it, the accounts which have been published 

 of the human hair changing its colour during the course of 

 a single night ; but we think the particular observations on 

 the ermine warrant us in believing, that the change of col- 

 our in the alpine hair is effected by a similar process. But 

 how is the change accomplished in birds ? 



" The young ptarmigans are mottled in their first plu- 

 mage similar to their parents. They become white in win- 

 ter, and again mottled in spring. These young birds, pro- 

 vided the change of colour is effected by moulting, must 

 produce three different coverings of feathers in the course 

 of ten months. This is a waste of vital energy, which we 

 do not suppose any bird in its wild state capable of sustain- 

 ing ; as moulting is the most debilitating process which 

 they undergo. In other birds of full age, two moultings 

 must be necessary. In these changes, the range of colour 

 is from blackish grey through grey to white, an arrange- 

 ment so nearly resembling that* which prevails in the er- 

 mine, that we are disposed to consider the change of colour 

 to take place in the old feathers, and not by the growth of 

 new plumage ; this change of colour being independent of 

 the ordinary annual moultings of the birds. 



" Independent of the support from analogy which the 

 ermine furnishes, we may observe, that the colours of other 

 parts of a bird vary according to the season. This is fre- 

 quently observable in the feet, legs, and bill. Now, since 

 a change takes place in the colouring secretions of these 



