122 NORTH AMERICAN MUSTELID^. 



of the hair, upon which the alteration of colour immediately 

 depends, the transition from the summer to the winter colours 

 is primarily occasioned by actual change of temperature, and 

 not by the mere advance of the season.'' The author quotes 

 in support of his views, and as tending to confirm them, the 

 observations of Mr. John Ilogg (Loudon's Mag. vol. v.), and 

 details an experiment upon a Lemming which turned white by 

 a few hours' exposure to severe cold. 



As a supporter of the view that the change results from 

 renewal of the coat may be cited the eminent naturalist Mr. 

 Blyth, who communicates his conclusions to Mr. Bell in these 

 terms {o}). cit. 153) : — ''Authors are wrong in what they have 

 advanced respecting the mode in which this animal changes 

 its color, at least in autumn j for in a specimen which I lately 

 examined, which was killed during its autumnal change, it was 

 clearly perceivable that the white hairs were all new, not the 

 brown changed in colour." 



Once again we have the minute and detailed observations of 

 Audubon and Bachman, made from March 6 to 28, upon an 

 animal thej^ kept in confinement, and which was observed dur- 

 ing this period to nearly complete the change from white to the 

 summer colors. These authors agree with Mr. Blyth: — "We 

 have arrived at the conclusion, that the animal sheds its coat 

 twice a year, i. e., at the periods when these semi-annual 

 changes take place. In autumn, the summer hair gradually 

 and almost imperceptibly drops out, and is succeeded by a 

 fresh coat of hair, which in the course of two or three weeks 

 becomes pure white ; while in the spring the animal undergoes 

 its change from white to brown in consequence of shedding its 

 winter coat, the new hairs then coming out brown." 



This confiicting testimony, which might be largely added to 

 if this were desirable, is perhaps not so difficult to harmonize 

 as it appears at first sight ; nor is it in the least required to 

 impugn the credibility of the witnesses of observed facts. I 

 should state in the beginning, however, that it seems to me to be 

 like straining a point to find any analogy between this periodi- 

 cally recurring change in a healthy animal and the tardy senile 

 change coincident with flagging of the vital energies, or with 

 the sudden pathological metamorphosis due to violent mental 

 emotions of a kind to which /<5r^e naturcc are not ordinarily ex- 

 posed. This point aside, I would readily agree with Mr. Bell 

 that subjection to sudden severe cold may materially hasten 



