42 THE GROWTH OF GROUPS 



from our Indian ones. Some rats received from an 

 Australian port were also of the same type. The 

 species we are dealing with seems to be of world-wide 

 distribution : its three most striking varieties are shown 

 in the frontispiece. It is an interesting fact that on 

 one occasion all three varieties were found together on 

 a ship. Since the mass of parasitic rodents in India 

 are of this kind, the term house rat will be applied to 

 them. 



The species Mus norvegicus, which is better known as 

 a house rat in Europe, is common also in some Indian 

 seaports, but it was not met with in the interior. It 

 was found to be constant in type, and therefore it will 

 not be further dealt with here ; the following class must, 

 however, be mentioned : 



Gunomys sp. There is in India a kind of rodent, which 

 is found burrowing in fields after the manner of a mole, 

 and is consequently known as the mole-rat. In taxonomic 

 literature this animal has appeared under various names. 

 In the " Fauna of British India " it is named Nesokia 

 bengalensis. Since 1907, however, it appears in the genus 

 Gunomys, which was defined by Mr. Oldfield Thomas. 

 From the taxonomist's point of view, Gunomys is a 

 composite group which has not yet been resolved into 

 its component species. Although mole-rats are rodents 

 of about the same size as M. rattus, they differ from that 

 species as regards all their superficial characteristics. 

 The length of the head and body, in the class, varies from 

 about 150 to 220 mm. The length of the tail is much 

 less than that of the head and body, being on the average 

 about 80 per cent, of it. The mole-rat is more stoutly 

 built than the house rat. Certain differences between 



