496 CLASS AVES. 



appear to be supported by any direct observations, nor is it 

 countenanced by any analogical reasonings. If we attend to 

 the mode in which the hair on the human head becomes gray 

 as we advance in years, it will not be difficult to perceive that 

 the change is not produced by the growth of new hair of a 

 Avhite colour, but by a change in the colour of the old hair. 

 Hence there will be found some hairs pale towards the middle 

 and white towards the extremity, while the base is of a dark 

 colour. Now, in ordinary cases, the hair of the human head, 

 unlike that of several of the inferior animals, is always dark at 

 the base, and still continues so during the change to gray : 

 hence we are disposed to conclude from analogy, that the 

 change of colour in those animals which become white in 

 winter, is effected, not by a renewal of the hair, but by a 

 change in the colour of the secretions of the rete raucosum, 

 by which the hair is nourished, or, perhaps, by that secretion 

 of the colouring matter being diminished or totally suspended, 

 " But as analogy is a dangerous instrument of investigation 

 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 furnished. The 

 appearances exhibited by a specimen of the ermine now before 

 us, are more satisfactory and convincing. It was shot on the 

 9th of 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 disappeared, in exchange for the 

 primrose-yellow, the ordinary tinge of those 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 hairs could be discerned. This 

 would certainly not have 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 



