4^8 On the Variation of the Weasel. 



tective value in such a case, when more than half the 

 winter a white coat would be exposed against a dark 

 background. In northern Vestergotland the ground is 

 covered with snow for about 72 days, and in Ostergotland 

 for about 85 days. In those provinces the white coat is 

 certainly more beneficial, although not to such a degree as 

 in Upland, with 103 days of snow-covered ground, and 

 still more further north (Lapland, with 189 days). The 

 climate seems, therefore, to afford an explanation why in 

 the north all weasels turn white, in the south none do so, 

 while in an intermediate region they occasionally turn white, 

 and sometimes remain brown during the winter. But when 

 there is no sharp limit, neither geographical nor clitiiato- 

 logical, and the brown and white weasels occur mixed in 

 the intermediate tracts, I cannot regard the establishing of a 

 subspecitic distinction on the difference in colour well founded. 

 With regard to size, the weasels, as is well known, are 

 subject to very great variation. This is shown in the most 

 evident manner by Hensel's valuable paper* "Craniologische 

 iStudien." As regards the present species, this author in- 

 forms us that the basal length of skulls of male weasels 

 varies from o9'8 to 32 4: mm., and their breadth over the 

 zygomatic arches from 25 to 18T mm. The great variation 

 in size of the skull of the weasel becomes evident from the 

 following table : — 



f English weasels I 



{Barrett- Hamilton) . . . . j 



German weasels {Hansel) 





Scaniau weasels (iu the j .) 



Museum of Lund accord-/ (^J^,^. gg 3^ ^^ ^^ 



mg to a communication f ^^^^^^ 

 L from Dr. 0. Holmquist). j '' 



s I Uplandic weasels (in the i 6 



•~^-( MuseumofUpsala,ion«- 1 (sexun- 32-5 % 18'5 15 



^- / t>erff) ) Known). 



This seems to indicate that the English weasels are 

 perhaps rather larger than those of the Continent, and that 



* Nor. Act. Acad. Leop.-Carol. Nat. Cur. t. xlii. (Halle, 1881). 



