No. 416.] VARIATION NOTES. 683 
6. The Long-Tailed Field Mouse! (Mus sylvaticus) has a distribu- 
tion which is almost coterminous with the limits of the Palearctic 
Region ; hence is a “ wide-ranging species” in Darwin’s sense. It 
is also an old species, for its bones are found in the cave deposits. 
It is much less variable than many other small mammals, and sports 
especially are rare. Thus it is a case against Darwin's law of the 
great variability of wide-ranging species and for Sedgwick's law of loss 
of variability in an old species. However, albinos (with pink eyes) 
have been noted as rare sports. The prevailing color is white below 
and more or less rufous above. Since the young are more like the 
house mouse in color, this color may be considered ancestral. The 
adult mouse becomes small and dark in certain isolated maritime 
localities (Lewis, Skye, Galway, and Kerry); a variation paralleled 
by that of squirrels, cattle, birds, the slugs, Limax, and butterflies. 
The mouse becomes rich-colored as it approaches the Oriental 
Region, — the home of rich-colored birds, — for example, at Kuatun. 
It is bright, clear-colored in the cold, drier regions of central Europe, 
just as the squirrel and red-backed vole are. 
! Barrett-Hamilton, G. E. H. On Geographical and Individual Variation in 
Mus sylvaticus and its Allies, Proc. Zool. Jour., pt. ii, pp. 387-428, London, 
August I, 1900 
