THE HOUSE MOUSE 637 



one of the palmar pads in size, and bearing a small flattened nail ; digit 

 3 is the longest finger, digit 4 being very slightly shorter ; digit 2 is 

 slightly shorter than digit 4, and digit 5 reaches a little beyond the 

 base of digit 4. The five palmar tubercles are small, occupying less 

 than half of the surface of the palm ; the three anterior are small and 

 round, the external one having a small additional free tubercle by its 

 outer side at the base of digit 5 ; the posterior pads are larger and oval. 

 Between the pads the skin is irregularly wrinkled and granular ; the 

 ventral surfaces of the digits have annular scales which tend to be 

 interrupted in the middle. 



The feet compared with those of the Field Mouse are shorter and 

 broader, and each has the usual six pads. The latter are relatively 

 small, and widely spaced, pf oval or rounded form, and differ but little 

 from each other in size — the two anterior being slightly the largest, 

 the postero-external slightly the smallest. In addition, a little free 

 supplementary tubercle is developed to the outer side of the pad at 

 the base of digit 5, and there is a similar tubercle to the inner side of 

 the pad, at the base of the hallux. The skin between the pads is 

 wrinkled, but smooth towards the heel. The hinder part of the sole is 

 hairy along the edges, and solitary hairs are scattered between the pads. 

 Digits 2, 3, and 4 are the longest, 2 and 4 being slightly shorter than 3 ; 

 digit 5 reaches a little beyond the base of digit 4, and digit i extends 

 as far as the base of digit 2. Both the fingers and toes (including the 

 hallux) are armed with small, simple, curved claws, those of the toes 

 being slightly the longer. 



The tail is usually about as long as, or a little longer than, the head 

 and body; it is finely annulated with about 180 scaly rings, the 

 boundaries of the individual scales being somewhat indefinite ; it is 

 clothed with numerous short, stiff hairs, each equalling in length the 

 width of about two and a half annulations ; the hairs do not, however, 

 conceal the rings, and they do not form a terminal pencil. 



The fur is soft throughout, longer, and denser on the back ; shorter, 

 thinner, and rather closely adpressed on the belly ; grooved bristles 

 occur as in the rats, but they are so slender as to produce no sensible 

 effect upon the quality of the pelage. The microscopic structure of the 

 hair is described below under Pigmentation and Inheritance. 



Colour: — The general colour of the upper parts is a dusky grey, 

 irregularly darkened with slate and black along the middle of the back, 

 and paling gradually to ashy grey on the flanks and belly. The hairs 

 have slaty bases, appearing on the surface in the region of the chin and 

 throat, and dusky tips ; their subterminal bands are yellow, and these 

 produce a more or less well-marked tinge of yellow above and below. 

 The ears are of a dull brownish colour, their antero-external edges 

 being usually darker than the other parts. The feet are dusky above, 

 VOL. II. 2 S 2 



