140 



RODENTS. 



spines. The genus is the largest in the whole mammalian class, comprising not 

 far short of a hundred and fifty species, which are distributed over the whole of 

 the Old World with the exception of Madagascar ; some of these, by human aid, 

 having now acquired a cosmopolitan range. With such a multitude of species, it 

 is of course only possible to allude to a few of the more interesting. 



The brown or, as it is often inappropriately called, the Norway rat 

 (M. decumanus), offers one of the most remarkable instances of a 

 successful usurpation to be found in the animal kingdom ; this creature having 

 ousted the black rat from most parts of England and a large area on the Continent, 

 So far as can be ascertained, its original home appears to have been Western China, 

 from whence it gradually travelled westward to'continental Europe, finally reach- 



B 



THE BROWN RAT (^ liat. size). 



ing the shores of the British Islands by the involuntary aid of ships. Its westerly 

 migration was, however, by no means limited to Europe, as it has been carried by 

 vessels across the Atlantic, and is now as abundant in many parts of North 

 America as it is in the Old World. The migration of the rat into Russia is known 

 to have taken place about 1727, in which year large troops of these animals 

 crossed the Volga from Central Asia, and made their way westwards. In Paris it 

 appeared about the middle of the eighteenth century, and it is generally supposed 

 to have first reached England in 1730. 



In appearance the brown rat is unfortunately too well known to need much 

 description, although it is advisable to point out the features by which it is 

 distinguished from its cousin the black rat. In form this species is characterised 

 by its heavy build, massive blunt muzzle, comparatively small ears, and relatively 

 short tail; the length of the tail being always less than that of the head and 



