640 MURID^— MUS 



land mice ; they are said to be very numerous among the crofts, but 

 after the corn is cut they betake themselves to the houses. 



The House Mice from Braescleit and Barvas, western Lewis, differ 

 in no way from ordinary musculus (W. Eagle Clarke, Ann. Scott. Nat. 

 Hist., 1908, 198; Hinton and Hony, The Scottish Naturalist, 1916, 221). 

 From fields at the Butt, or northern extremity, of Lewis, Eagle Clarke, 

 however, obtained specimens which approach muralis in their large 

 size, but do not differ from musculus in coloration or in skull structure. 



On North Uist ordinary House Mice, and others which are practically 

 identical with muralis in size and colour, though slightly paler below, 

 occur quite commonly in the houses at Lochmaddy. Intermediates 

 between the two forms have not been observed, and although the only 

 but imperfect skull seen seems to agree better in form with that of 

 musculus than with that of muralis, it is not impossible that the variety 

 may be a second form of the latter species (Eagle Clarke, op. cit.). 



A youngish female from Islay has the whole ventral surface of a 

 beautiful clear white, separated by sharp lines of demarcation from 

 the flanks, which are but slightly lighter than the back, the general dorsal 

 colour approaching that of Apodemus (Hinton, Ann. Mag. Nat. Hist., 

 July 1914, 130, and June 1915, 583). Specimens from Skye, and a male 

 from Tiree {Proc. Zool. Soc, 191 3, 835) trapped in sand-hills, represent 

 the yellowish outdoor form, while one obtained by Mr Kinnear in 

 Barra, fron^ a hole in a field, is of normal indoor appearance. 



Specimens obtained for Ogilvie-Grant from Hermaness Hill, North 

 Unst, Shetland, in the autumn of 1914, are remarkable merely for 

 their relatively stout tails. 



Exceptional variation : — Quite apart from the well-known differ- 

 ences in pattern and colour presented by the tame " fancy " breeds, the 

 House Mouse shows many individual or family variations, particularly in 

 its coloration and pelage. Such variations have formed the bases of most 

 of the specific or sub-specific names enumerated in the synonymy above. 



True albinos, wholly white or cream-coloured with pink eyes, 

 partial albinos, white specimens with dark spots, dark specimens with 

 light spots, and melanistic examples, are not rare. Fatio's M . poschiavinus 

 was based, with much hesitation, on a Swiss melanic race. 



Tomes (in Bell, ed. ii., 296) describes a great number "killed in 

 a wheat-rick at Welford-on-Avon, which were of a light grey colour, 

 without the least mixture of brown," and Collett (165) speaks of a 

 similar variety in Norway. In another rick at Welford Hill, Tomes 

 found all the mice to be " of an unusually dark colour, especially along 

 the dorsal line, which was nearly black " ; this latter form is apparently 

 that to which the names " Rick Mouse " and " Barn Mouse " are 

 applied (Tomes, op. cit., 300), and which occasionally, though not 

 always, attains an unusually large size. 



