320 



THE NATURE BOOK 



grey or ^vhite. besides being prone to 

 albinism. Generally speaking, however, 

 the Water Shrew Mouse is blue-black in 

 colour ; the Common Shrew Mouse a rich 

 warm brown ; and the Pygmy a colder 

 brown suffused with a tinge of purple. 

 Both the Water Shrew Mouse and the 

 Common Shrew Mouse occasionally have 

 white fringes on their ears, and there 

 is frequently a cinnamon band on the 

 flanks of the Common Shrew Mouse 



nils. 



wer Jaws. 



Scapula (shoul- 

 der blade). 



Clavicle (coll_r 

 bone). 



Humerus (upper 

 arm bone). 



Bones cf fore- 

 arm and hand. 



SKULLS AND BONES OF THE FOKE-LIMBS OF 



1. A PySmy Shrew Mou^e. 



2. An Immature Common Shrew Mouse. 



3. A Mature Common Shrew Mouse. 



^vhich I have nexer found on the Pygmy. 

 The belly of the Water Shrew Mouse is 

 sometimes })ure white, with a sharp line 

 of demarcation (the white is often super- 

 ficially stained by continual contact with 

 muddy surroundings), and sometimes blue- 

 grey. I have taken the two varieties in 

 about equal numbers. The snout of the 

 Water Shrew Mouse is distinctly more 

 blunt than that of the two other species. 



The above external features should 

 suffice to distinguish adults of the three 

 species, while there are certain anatomical 

 differences in the Water Shrew Mouse 

 (he has two teeth less, for example), 

 which make his claim to being a good 

 si>eries indisjmtalile. 



When, however, we come to compare 



the Pygmy, the immature Common Shrew 

 Mouse, and the immature Water ShrexV 

 Mouse, our task becomes more difficult, 

 and is complicated by the fact that an 

 immature Water Shrew Mouse presents 

 occasionally a brown-black rather than a 

 blue-black coloration. His muzzle, how- 

 ever, is characteristically blunt, so that 

 our real difficulty commences w'hen we 

 endeavour to distinguish the immature 

 Common Shrew Mouse from the Pygmy. 

 This distinction can only be effected by 

 careful external and internal measure- 

 ments, for the Pvgmy and the immature 

 Common Shrew Mouse are often identical 

 in colour, and so far as all-over body length 

 and tail length are concerned, often 

 identical in size. When, however, we 

 commence to study the external dimen- 

 sions of the former more carefully, and, 

 carrying our investigation a little further, 

 to take careful measurements of his bones 

 and of his teeth, we find that every bone 

 in his body and every tooth in his head is 

 considerably smaller than the corre- 

 sponding bone or tooth in an immature 

 Common Shrew Mouse of approximately 

 the same length. The P^^gmy is, in 

 fact, a miniature edition of the adult 

 Common Shrew Mouse. He is exquisitely 

 proportioned, and displays none of the 

 legginess and want of balance which is 

 characteristic of a young animal. I am 

 not aware of the existence of any ana- 

 tomical distinction whatever between the 

 two species, apart from these distinctions 

 of size. It is said that the Pygmy 

 Shrew Mouse is the only member of the 

 family which occurs in Ireland. If this 

 be the case, it would seem as if a mild 

 climate, by favouring an earlier maturity, 

 had influenced his evolution, and it would 

 be interesting to know the mean annual 

 rainfall and temperature of the different 

 portions of the Old World, ranging 

 East as far as Saghalien, from which he 

 has been reported. In this country i 

 have found him where\-er I have found 

 the Common Shrew Mouse, and in equal 

 abundance, though, as might be expected, 

 he is more difficult to trap. 



So far as breeding, feeding, movement, ' 

 and general habits are concerned, I 

 have not been able to detect any difference 

 between these two species. The Water 

 Shrew Mouse presents, as might be 



