68 THE GROWTH OF GROUPS 



a serial register. The points observed were those that 

 might help the Commission in its task, such as the number 

 of fleas on each rat, the pathological condition, the state 

 of pregnancy, etc. For the biologist, it is fortunate 

 that any peculiarity of the outward appearance of the 

 rats, as well as the place of residence of each of them, 

 were included among the records. It is evident that the 

 peculiarities which would be noted under these conditions 

 would be of an obvious kind. Minute details of propor- 

 tion and tint, such as are often the subject of inquiry 

 among zoologists, would in all probability be overlooked 

 by observers whose chief interest lay in other directions. 

 The peculiarities which were noticed and recorded were 

 indeed of a kind such as could be seen at a glance and 

 from a considerable distance. This is well, since the 

 common conception of a species is of something distinct 

 at a glance. 



The house rats of Poona as a class have no special 

 peculiarities. They are, on the average, slightly smaller 

 and darker than the rats of Bombay and other cities. 

 They are of the whole-coloured brown type, and are 

 less variable than those of Bombay city, where the black 

 and the white-bellied varieties are comparatively common. 

 At Poona, among all the rats caught during the year, 

 there was not a single black one, and there were only 

 nineteen of the white-bellied variety. Of these nineteen, 

 three were caught while I was at Poona. This was not 

 due to chance, but to the fact that traps were specially 

 set at my request in those houses from which white- 

 bellied rats had previously been captured. 



The white-bellied rats of Poona are exactly like the 

 common ones, except for the one peculiar character 



