38 



Rats and Mice 



Ears moderately large, covering the eyes when pressed for- 

 ward, clothed almost everywhere with short fine hairs. 



Tail about as long as the combined length of the head and 

 body ; frequently longer, rarely shorter. 



Feet short and broad. In the hind-foot a small supplementary 

 pad is present on each side near the lateral margins of the pads at 

 the bases of the innermost and outermost toes. 



Fu7' soft, intermixed with grooved bristles as in the rats, but 

 these bristles are too slender to affect sensibly the quality of 

 the coat. 



Teats : females with ten mammae, three pairs on the chest, 

 two pairs towards the groin. 

 Colour variable. 



Indoor specimens are usually dusky grey above, more or less 

 darkened by slate or black along the middle of the back, and 

 gradually paling on the sides to the ashy grey of the underparts ; 

 ears brownish ; feet dusky above, not contrasting with back ; tail 

 dull brown, occasionally lighter below than above. 



Outdoor specimens have the hair-tips often more or less ex- 

 tensively bleached to a yellowish brown ; so that such specimens 

 usually appear more or less sandy or tawny in colour. 



Albino and melanistic specimens are not uncommon. In 

 domestication numerous varieties of colour and pattern have been 

 produced as fancy breeds. 



Weight of adults normally about 16 grammes, or slightly over 

 J ounce. 



Measurements in millimetres : — 



Hind- foot, 



Head and Body. Tail. without claws. Ear, from base. 



70 to 100 70 to 102 17 to 19-4 11 to 16 

 In its outdoor dress this animal may sometimes be confused 

 with the Long-tailed Field Mouse ; its shorter, broader, and 

 dusky feet, and smaller and less protruding eyes are diagnostic. 

 The skull and teeth (Figs. 5 and 6, pp. 57-59) are so peculiar that 

 they cannot be confused with those of any other British species. 



History. — Like the rats, the House Mouse appears to be of 

 Asiatic origin. Its arrival in Europe dates, however, from a very 

 remote period. It was well known to the ancient Greek and 

 Eoman writers, and it figures in our own records and literature 

 for more than one thousand years. On certain islands, such as 

 St. Kilda and the Faeroes, it has existed long enough to develop 



