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Show 1900.] MUS SYLVATICUS AND ITS ALLIES. 397 in Transylvania, while it only differs from the var. rupicola in being unicoloured above. In fact the variety rupicola itself would seem to be another case in point, being found, as it is in Lessona and Pollinera, up to a height of 7000 feet in the Piedmontese Alps, as well as in the Mourne Mountains of Ireland, from which it has been recorded by Mr. W . D. Boebuck. From whatever point of view we regard the numerous forms of Mus sglvaticus, it is of extreme interest to find that the changes and variations in different climates are parallelled, to a certain extent at least, not only by other mammals, but by birds and, in some cases, by invertebrates. In a recent paper' I showed that the brightening of the colours of certain birds according as they range southwards is parallelled by the Weasel, Putorius nivalis Linnaeus and its subspecies. So, too, the most richly coloured subspecies of 31us sylvaticus which 1 have seen is 31us s. draco from Kuatun, a locality which must be near the extreme south-eastern limit of the range of the species, while in the south-west the deep, almost chocolate upperside of the single British Museum specimen of 31. s. algirus of Algeria seems to be suggestive of a similar tendency. It is also of interest to find that the bright, clearly coloured Mus sglvaticus of the cold drier regions of Central Europe is the counterpart of the corresponding form of Squirrel, Sciurus vulgaris rufus Kerr; whereas the duller subspecies of some of the damper Western regions are parallelled by S. v. leucourus Kerr and S. v. tgpicus Linnaeus ; and other parallels may be sought amongst the Bed-backed Voles (Evotomys) and their subspecies. W e are only just beginning to obtain any general light on the distribution of variation amongst European mammals, but the larger size of Mus s. princeps of Central Europe finds a parallel in at least one other species, viz. Lepus europceus typicus Pall., of which the Central European and Eussian examples are distinctly larger than the Western, L. e. occidentcdis de Winton 2. Indeed, it would be easy to quote a good many other instances, taken from birds as well as mammals, which seem to afford evidence of some law of decrease in size from cold and clear to warmer and duller regions. Finally, the occurrence of especially dark and often small forms in various isolated western localities of the British Islands finds an abundant counterpart in other groups. I may point to the Lepidoptera, amongst which so many dark western varieties have been recorded ; to the dark Squirrels of damp mountainous continental regions ; to our small dark breeds of cattle (Scotch, Irish, and Welsh); and to numerous instances amongst birds, as the Dippers (Cinclus) and the Long-tailed Titmice (Acredula). Perhaps the most interesting parallel of all is afforded by the Song-Thrush, Turdus musicus3, of which it is stated that individuals which inhabit the 1 Ann. & Mag. Nat. Hist, (7) v. p. 42 (1900). 2 See Mr. W . E. de Winton's paper, "On the Hares of Western Europe and North Africa," in Ann. & Mag. Nat. Hist. ser. 7, vol. i. February 1898. 3 Howard Saunders, ' Manual of British Birds,' ed. iv. p. 3. |
