3o6 THE BOOK OF THE ANIMAL KINGDOM 



instead of Rabbits, the Dutch Boers utilize the beast for the purpose 

 of keeping down Rats and Mice. 



ORKIfET VOLE.— This interesting Vole (Fig. 251) was first noticed 

 by the well-known naturalist, Mr. J. G. Millais, son of the famous 

 artist, in the Orkneys in August 1886. It was a most unexpected 

 discovery in British mammalogy, and only goes to prove how 

 important it is to pay intelligent attention to any animal that is 

 encountered which presents any divergence from the recognized 

 type. Mr. Millais was first attracted to the Orkney Vole by reason 

 of its dark appearance and its large size, and a comparison between 

 it and its common mainland relative will reveal the broad, blunt and 

 heavily furred head of the Orcadian species, while the incisor teeth 

 are different in size, and the molar teeth are of a different pattern. 

 It seems curious that whilst a boreal Vole is found in the Orkney 

 Islands the same is absent from the Shetlands, and a further point of 

 interest to which notice may be drawn is, that in the case of this 

 newly discovered British mammal the general rule of island forms 

 being smaller animals than those found on the mainland is reversed, 

 for instead of the Orkney animal being smaller than its mainland 

 cousin, it is decidedly larger over the whole of the body, with the 

 sole exception of the tail, which is about the same size. The Orkney 

 Vole is almost twice the size of the Common Field Vole, and the 

 general colour is dull sandy-brown. 



There can be no doubt that if more attention were devoted to 

 insular faunas and floras much valuable data would result. This 

 has been carried out in Ireland by enthusiastic naturalists there with 

 great success during recent years, and their excellent work might 

 well be followed up by other naturalists in all parts of the world 

 where it is possible to carry out similar undertakings. 



OERBILS. — The Gerbils are small Rodents which are at once 

 distinguished by having long hind-limbs and long, hairy tails, and 

 they remind one in appearance and habits of the Jerboas. They are, 

 however, distinct from the last-mentioned animals in regard to the 

 muzzle, eyes, toes on the hind-feet, and teeth. 



There are a large number of different species of Gerbils found in 

 both Africa and Asia, and the illustration (Fig. 252) shows the Cape 

 Gerbil. This species is not so well known as its Indian cousin, and 

 it is the latter that had best be described. This may be compared 

 in size to the Brown Rat. It is brownish-rufous on the upper parts 

 and white below; it has large, bright eyes, a long, tufted tail, and, 



