152 RODENTIA 



of which will be given under the various species. The Common 

 Rat, as well as some exotic species, have recently attained an 

 even more unenviable notoriety, since the discovery that they 

 are the bearers of the disease of the above name to human beings. 



From the point of view of the philosophical naturalist, the 

 rodents are in many ways the most attractive order of British 

 mammals. They usually possess a high degree of beauty, both 

 in form and colour, and within their own limits their variety is 

 almost infinite. It is noticeable, for instance, that the order is 

 so plastic that it includes within its ranks several species and 

 sub-species peculiar to Britain. The history of all of these is 

 of special interest. 



Amongst the mice there are distinct representatives of 

 specific or sub-specific value in Fair Island, the Orkneys, 

 St Kilda, the Outer Hebrides, and Skomer Island. Almost all 

 the other small rodents of Britain are sub-specifically distinguish- 

 able from their representatives on the continent of Europe. 



In the matter of pelage the rodents are in many ways 

 remarkable. The varying hares afford conspicuous instances 

 of the phenomenon of winter whitening, the Squirrel of bleach- 

 ing and of a complicated system of moults, the water and true 

 rats of a tendency to melanism.^ In some families, as in the 

 LeporidcB and the South American chinchillas, the fur is of very 

 fine texture, but in other forms it is replaced by spines on the 

 back, the most extreme instance being that of the (non-British) 

 porcupines. 



The Dormouse is subject to hibernation. The Brown Rat 

 and House- Mouse are so closely attached to man as to be 

 almost domestic. The former is admittedly a recent arrival, 

 yet the locality of its origin is unknown. The Rabbit is also 

 not indigenous, although known at least from the twelfth 

 century. 



A number of other rodents inhabited the British Islands in 

 past geological ages, and some of these are still represented by 

 their descendants on the continent of Europe. 



Structure: — The prominent cutting incisors often excite 

 interest by the remarkable deformities or abnormalities which 

 they undergo when injured. Since the pulp is persistent, these 



^ See also, for the colour of certain exotic squirrels, below under genus Sciurus. 



