66 



Records of the Indian Museum. 



[Vol. lU, 



nature of the rat population. There are six main thoroughfares in 

 this city lying parallel with the river. They are crossed at right 

 angles by a series of lesser streets which receive numerical designa- 

 tion. In any two of these streets the back walls of the houses are 

 separated by an open space some twelve feet in width, a receptacle 

 for rubbish, which is removed daily. These intervals between the 

 rows of houses are spoken of as the " back drainage spaces." 



An estimation of the numbers of the different species received 

 at the collecting stations on six occasions was made. It must be 

 remembered, however, that such estimations can only approx- 

 imately represent the proportionate numbers of the different species 

 actually present in the city. Doubtless some sorts of rats are 

 to be captured more easily than others. The distribution of the 

 several species must differ in certain parts of the town ; for example, 

 the specimens of Mus decumanus generally came from riverside 

 buildings. 



The groups into which the rats have been here divided are, 

 from the systematist's point of view, of the widest sort. Mus 

 rattus and M. concolor (the miniature rattus of Burma) have for the 

 purposes of this estimation been included in one group, for 

 although this group contains at least two races, numerous indivi- 

 duals were met with which in size were intermediate between the two. 



In the group of Gunomys are included at least two w^ell-marked 

 races, though many more would be recognised by some systematists. 

 Care was taken to exclude all but adults from the reckoning, for 

 the half-grown Mus decumanus is often difficult to distinguish from 

 a young Nesokia by superficial examination ; the same precaution 

 was necessary in deahng with the rattus group. 



Rats were received at the collecting stations at specified times. 

 All the adult rats received at one time were counted on six occasions. 

 Those received on each occasion have been shown separately, as the 

 numbers differ considerably. 



