108 Records of the Indian Museum. [VoL. V, 
conspicuous ; so Conspicuous are they among the others that it is 
the custom of the Plague Commissioners to refer to them for con- 
venience as Mus alexandrinus as a nominal distinction from the 
common Mus rattus. This is in accordance with the modern use of 
the word ‘‘ species,’’ for two animals which appear different from 
one another at a glance are usually considered to be of different 
species. The name M. alexandrinus, as used in this particular 
case, might, however, be regarded by a systematist as calling for 
correction ; it is, therefore, preferable to use the term white-bellied 
variety. The map, plate x, shows exactly how far this variety is 
established in the city of Poona ; it must be remembered that forty- 
five thousand whole-coloured rats have been taken from the city at 
large and that there is scarcely a house which has not contributed 
to the total. The nineteen white-bellied rats were caught in nine 
houses ; four of these were contiguous and two others are separated 
from them by the width of a street. Six of the houses therefore 
form a distinct focus of habitation for rats of this special variety. 
The other three houses form another centre, perhaps more than one, 
which is situated about 250 yards further south. 
The following table is an extract from the register and shows 
the order in which the rats were caught. The reality of the foci 
became gradually recognised as the trapping was continued in 
every part of the city. 
House. Reference to map. W.B. rats. 
Raiwar 380 I 3 
33 - 2 
- 963 3 2 
1146 4 I 
8 IIQI 5 2 
a. 5s) 6 2 
381 7 2 
s: 382 8 3 
<5 379 9 2 
1g 
The serial numbers I to 9 refer to the order of capture of the 
tats and indicate the particular houses on the map. ‘he focus 
which is represented by the six houses, 379—382, 553, 963, Raiwar, 
contributed fourteen rats, but this fact does not give us a true idea 
of the size of the colony ;—if two or three rats are caught in a house 
their companions become wary and avoid the traps. In all 
probability this particular colony numbered a hundred or more 
individuals. 
We therefore arrive at the following conclusions: Poona is a 
large town with a rat population of a million or more. The nature 
of this population has been fairly sampled by subtracting 45,000 
of them from all parts of the city ; the rats are for the most part 
sf the whole-coloured brown type, but established in the heart 
of the city is a colony of white-bellied rats which contains in al! 
