648 MURIDAZ—MUS 
of the North African element in the Portuguese fauna.” In the 
eastern Mediterranean region JV. gentzl’s, Brants, and in southern Asia, 
M. bactrianus, Blyth, apparently represent the same group of wild, light- 
bellied House Mice. 
It cannot be said that our knowledge of the status of the forms 
mentioned above is in a very satisfactory state. The characters by 
which these forms are distinguished from JZ. musculus are for the most 
part of trivial importance, and hardly sufficient to raise these mice 
above the rank of sub-species of musculus. The forms in question, 
however, seem to have found their way to Europe at very different 
times, by different routes, and in different ways; some, like spzczlegus, 
have spread westwards and northwards naturally, while others, like 
musculus, have travelled as the constant companions of man. More- 
over, it is just possible, as noticed above, that the genus was present 
here during part of the Pleistocene ; and if this be so, either J7. muralis, 
Jeroensis, or spicilegus, or all three, may be the descendants of this 
ancient stock. For the present, therefore, pending further research 
upon the very difficult problems involved, it would seem better to 
follow the somewhat delicate classification adopted by Miller, than to 
group all these forms as mere sub-species of sasculus. 
A systematic study of the American colonies of Mas and Epzmys 
might yield important information concerning the mechanics of 
geographical variation. The absence of native J/urzn@ from the New 
World eliminates one of the chief difficulties attending such research in 
the Old World; for, in the latter, we cannot ascertain to what extent 
newcomers have blended with indigenous species of these genera in 
any given region. J. A. Allen (Bull. Am. Mus. Nat. Hest, 1894, 175; 
1895, 236; 1896, 59; 1897, 35, 116, 198 (Allen and Chapman); 1899, 8; 
1903, 540; 1904, 435; and 1910, 101) has given detailed descriptions of 
many American specimens of J/ws. House Mice from Cajabamba, 
Peru, showed a strong tinge of rusty buff, and similarly coloured 
examples are before us from Ecuador and Cordoba, Argentina; those 
from Santa Marta, Colombia, were also rather more fulvous above and 
below than are normal specimens from the United States; those from 
San José, Costa Rica, were unusually pallid. In Texas and Arizona 
the species lives, in many places, a quite wild life, and is developing a 
remarkably red coloration. House Mice were found at Jalapa, Vera 
Cruz, inhabiting “old fields” in company with native rodents; these 
mice have been recognised by Allen and Chapman as forming a distinct 
sub-species, their JZ. musculus jalape, characterised by having the mid- 
dorsal region and tail of a uniform deep black throughout, the sides 
yellowish-grey, or ordinary mouse colour, the belly pale buffy grey, 
and the feet and ears dark brown. Similarly, dark coloured mice, 
perhaps belonging to the same sub-species, occur in Nicaragua. Winge 
