74 



THE GROWTH OF GROUPS 



following manner. Numerous persons in India were 

 requested to send specimens of the common rats of their 

 district. It is evident that such a request may be 

 answered in different ways. One correspondent, living 

 in a town where rats are not being destroyed as a sanitary 

 precaution, will probably set a few traps and send the 

 first two or three animals that are caught in them. If 

 these should happen to be of the white-bellied variety, 

 we cannot assume that all the rats of the district are like 

 them. Another correspondent in a plague-stricken dis- 

 trict, seeing hundreds of rats daily, will probably make 

 a selection to illustrate the colour varieties known to him, 

 but the relative numbers of the kinds sent will not neces- 

 sarily be in proportion to the numbers of the kinds actually 

 present in the district. These facts should be borne in 

 mind in perusing the following table. In most cases 

 when the number sent is more than ten, the rats are 

 from a place where there was opportunity for selection 

 from among large numbers. The records from Belgaum, 

 Poona, and Dacca were furnished by members of the 

 Plague Commission. 



