THE HOUSE MOUSE 647 
Geographical variation :—Of the seven European forms of J/us 
recognised by Miller, two only are referred by him to IZ. musculus, 
viz.: JJ. m. musculus, described above, and MZ. m. azoricus, Schinz, 
inhabiting the Azores and the Mediterranean region. The latter 
sub-species is distinguished from the typical form by its lighter and 
yellower back, and its buffy grey, instead of dusky grey belly. It 
may be regarded merely as a phase of coloration appropriate to a 
sunnier climate, and the gap between it and the dusky indoor animal 
of northern countries is, at least, partly bridged by our more pallid out- 
door individuals. Winge (of. cz¢., 89) states that at present the wild- 
coloured race is the common one in Denmark; he adds that formerly 
the dusky indoor form has certainly been preponderant. Two insular 
forms, WZ. muralis and M. feroensis, from St Kilda and the Feroes 
respectively, are accorded full specific rank by Miller; these are dis- 
cussed below. 
The remaining three European members of the genus are treated 
by Miller as sub-species of M. spictlegus, Petényi, described from 
Hungary. This species differs from J. musculus in its smaller size 
(condylo-basal length of skull rarely attaining 21; hind foot usually 
between 15 and 17 mm.); in having the tail nearly always noticeably 
shorter than the head and body, the under parts whitish and sharply 
contrasted with the flanks, and the notch of the upper incisor less 
developed. The typical form, characterised by its clear greyish-brown 
upper parts, ranges from the northern part of the Balkan Peninsula to 
the Baltic, and westwards into southern Sweden. Its representative in 
central and southern Spain is J. s. hispanicus, Miller, in which the 
dorsal colour is “buffy, or pale buffy grey.” The third sub-species is 
M. s. lusitanicus, Miller, known only from Cintra, Portugal; in this the 
upper parts are brownish-grey, and show a decided tinge of russet. 
Both Thomas (Zoo/ogist, 1896, 137), who first discovered J. spicilegus 
in Portugal and afterwards in the Balearic Islands, and Miller 
(Catalogue, 877) regard this species as truly indigenous to the Mediter- 
ranean region. It leads a perfectly wild life in fields, scrub, and open, 
dry forest, and it thus affords in station and coloration a close parallel 
to Hpimys rattus frugivorus. It appears to be the natural representa- 
tive in Europe of J. spretus, Lataste,) from North Africa; and 
Thomas states that “like the Mungoose and the Genet, it forms part 
282, iii, 1 (Japanese Waltzing Mice crossed with European albinos) ; Durham, Ref. 
Evol. Comm. Roy. Soc., iv., 41, 1908; Hagedoorn, Univ. California Pub. Physiol., 
lil., 1909, 95; Zettsch. indukt. Abstammungslehre, Berlin, 6, 1912, 97; and Little, 
Washington Carnegie Inst., Pub, No. 179, 1913, II. 
1 Actes Soc. Linn., Bordeaux, 1883, 17 ; but later (Cat. crit, Mamm. Tunis, Paris, 
1887, 22) Lataste himself recognised that MZ. spretus “is, perhaps, only a very 
aberrant variety of the House Mouse.” 
