OCR Text |
Show 1900.] MUS SYLVATICUS AND ITS ALLIES. 395 and Barra (31. s. hebridensis) and St. Kilda (31. s. hirtensis), where it is accompanied by a very interesting shortening of the ear and lengthening of the foot proportionately to the length of the body. A representative of the large form occurs also in the Shetlands ; but m y series is not sufficiently good to enable m e to decide finally as to its affiuities. The Iberian Peninsula and Morocco seem to be the habitat of a large dull-coloured form, with regard to the exact appearance and relationship of which, in default of more numerous specimens, I am a little uncertain, and for the present can merely allude to it under the name Mus hayi Waterhouse. To turn to the smaller subspecies (31. s. intermedins), this is found mainly in the British Islands and in the neighbouring continental areas of Holland, Belgium, and North-west France; but the exact limits of its distribution are as yet uncertain, and it probably intergrades in all directions with other subspecies. It is extremely interesting to find that specimens from such damp western localities as Lewis and Skye in the Scotch Islands, Galvvay and Kerry in Ireland, and Oporto in Portugal indicate that in such situations the reduction of size and darkening of the colour of the upper surface reaches its maximum. It is not less interesting to find some evidence that there may be two ways of attaining to that greater dullness of coloration which seems to be fitted to a sojourn in the moderately warm, damp regions of Western Europe ; aud that, whereas in M. s. hebridensis and 31. s. hirtensis this object is attained by rendering more uniform, although not darker, the colour of the upper surface, by the enlargement of the breast-band, the partial obliteration of the line of demarcation between the two surfaces of the body, and the extension of the yellow colour to the belly, the whole consistent with a retention of large size, in 31. s. celticus the same result is brought about by an increase of the black-tipped hairs on the back, while the belly, although retaining its pure whiteness, is made Jess conspicuous by reduction of the size of the animal. The occurrence of representatives of each of these forms almost side by side on the small island of Lewis is perplexing; but Mr. de Winton informs m e that the larger 31. s. hebridensis keeps severely to itself ou the western side of the island, and that he believes that the presence of the smaller form may here be due to accidental introduction. As regards the remaining forms, such as 31. s. islandicus, arianus, pallipes, griseus, chevrieri, draco, and 31. argenteus, little is known and little can be said ; but there is evidence to show that the representatives of 31. sglvalicus are characterized in the uorth (according to Badde) by larger, and in the south by smaller size, and in the latter case by a proportionately smaller hind foot. The thick fur and light upperside of M. s. pallipes seem to indicate a development to suit great cold, combined perhaps with desert-or steppe-like conditions ; but the curious differences between the manner in which the young grow up in extremes, such as M. s. draco and 31. s. into medius, are at present inexplicable. |