1910. ] R. E. Lnoyvp: The Races of Indian Rats. 109 
probability a hundred or more individuals ; this is inferred because 
six adjacent houses are known to contain them. and, so far as could 
be ascertained, no others. 
The question now arises as to how this state of affairs came 
about. The progenitors of the colony were either born in the city 
from normal parents or they are migrants of another race which 
arrived from without. In my opinion it is unnecessary to discuss 
the probability or possibility of the founders of the colony creeping 
unobserved into the heart of the town or arriving there in corn 
sacks, since we do not know whencesoever they can have come. 
There is no extensive area in India which is inhabited by a pure 
race of white-bellied rats. They are to be found in isolated groups 
side by side with the commoner whole-coloured rats in several parts 
of the Peninsula, especially in the south-eastern part of Madras, 
but there is no particular centre from which they can have 
migrated. 
Case 2.—It was mentioned previously, that rats are occasion- 
ally found which are marked with a pure white line in the middle of 
the breast. The same kind of sport has been noticed in Bombay , 
Madras, Nowgong and Calcutta. At Poona I obtained four half- 
grown rats which were caught together in a trap. All of them 
have this breast mark, they are exactly in the same stage of ado- 
lescence and are obviously of the same litter ; an adult rat showing 
the same character was caught in another trap close by. These 
rats are shown in the photograph, plate 1x. This case helps to 
prove that, however such a character originates, it is passed on to all 
the members of a litter in the succeeding generations, and by 
analogy it helps us to understand how the group of white-bellied 
rats which were established in the six contiguous houses came into 
being. There is no apparent relation between the white breast 
mark, as a character unit, and albiventralismassuch. Intermediate 
forms, showing a widening and lengthening of the breast line and 
bridging over the gap between the two extremes, were not found in 
Poona. In some parts of India, for ‘example in Simla, rats have 
been found which are marked with variable patches of white on the 
abdomen (zbid., pages 37, 38). The white breast line appears to be 
a definite character, not only among Indian rats, but among those 
of other countries. The species ‘* Mus hibernicus ’’ was established 
to commemorate a group of black rats which was found in Ireland. 
It has been shown that this species is a melanotic variety of Mus 
decumanus plus a white breast line. The published illustration of 
the skull of the Irish rat might indeed have been drawn from any 
Mus decumanus such as is common in Bombay and Calcutta. A 
white breast line occurs in animals other than rodents, for example 
in dogs. 
Nains Tal. 
A second visit to this place has enabled me to confirm the 
previous conclusions (2b7d., pages 38, 89), but in one respect to correct 
them. Since plague preventative measures were not in foree a+ 
