24 PHILOSOPHY OF ZOOLOGY. 



disposed to conclude from analogy, that the change of col- 

 our, in those animals which become white in winter, is ef- 

 fected, not by a renewal of the hair, but by a change in the 

 colour of die secretions of the rete mucosum, by which the 

 hair is nourished, or perhaps by that secretion of the 

 colouring matter being diminislied, or totally suspended. 



" But as analogy is a dangerous instrument of investiga- 

 tion in those departments of knowledge which ultimately rest 

 on experiment or observation, so we are not disposed to lay 

 much stress on the preceding argument which it has fur- 

 nished. The appearances exhibited by a specimen of the 

 ermine now before us are more satisfactory and convincing. 

 It was shot on the 9th May (1814), in a garb intermediate 

 between its winter and summer dress. In the belly, and 

 all the under parts, the white colour had nearly disappear- 

 ed, in exchange for the primrose-yellow, the ordinary tinge 

 of these parts in summer. The upper parts had not fully 

 acquired their ordinary summer colour, which is a deep 

 yellowish-brown. There were still several white spots, and 

 not a few with a tinge of yellow. Upon examining those 

 white and yellow spots, not a trace of interspersed new short 

 brown hair could be decerned. This would certainly not 

 liave been the case if the change of colour is effected by a 

 change of fur. Besides, while some parts of the fur on the 

 back had acquired their proper colour, even in those parts 

 numerous hairs could be observed of a wax-yellow, and in 

 i^l the intermediate stages from yellowish-brown, through 

 yellow, to white. 



" These observations leave little room to doubt, that the 

 change of colour takes place in the old hair, and that the 

 change from white to brown passes through y<>llow. ' If 

 this conclusion is not admitted, then we must suppose that 

 this animal casts its hair at least seven times in the year. 

 In spring, it must produce primrose-yellow hair ; then hair 



