fee oe URE ERS Oto. BR VA LT ONS. ON THE 
RACES Orr. T NDT A IN® (ROAETS». 
Dy RK. LLOvD, (MBs. DSc. Professor’ of Biology, Medical 
College, Calcutta. 
In a recent number of the Records of the Indian Museum (vol. 
iii, pt. I, 1909) I brought forward some evidence in favour of the opin- 
ion Prat discontinuous variation plays an all-important part in the 
production of new races. ‘The observations on which this evidence 
was based were made upon some thousands of common house rats, 
which had been captured in many parts of India. The subject 
may be summarized as follows :— 
It was found that the common house rats of India are, in a 
broad sense, of one species. It is not possible to find any sure cri- 
terion by w hich a house rat caught in the Punjab can be distinguished 
from one caught in Bombay or Bengal: but taken indiv idually , 
the rats of any particular town are sometimes different from one 
another, especially in the kind and distribution of the pigment 
which determines their coat colour. Some of the differences, to 
which I refer, are of such magnitude that those specimens w nich 
exhibit them, can be distinenished from one another even at a 
distance of thirty yards in a “ean light. The common house rats 
of India are of the type long known by the name of Mus vattus ; 
they are usually of a dull pow n colour which is somewhat lighter 
on the ventral surface. 
In many Indian towns, thousands of house rats have been 
captured for sanitary purposes, and there is no doubt that the 
whole-coloured brown type is predominant. But sometimes other 
varieties are found along with the common kind. Of these other 
varieties, the commonest by far is one in which the fur of the whole 
ventral surface. of the belly, breast, throat and chin is pure white, 
the whiteness being sharply defined from the brown colour of the 
sides. Another less common variety is wholly black. In another 
variety the tail is partially white, in others there is a white patch 
on the forehead, or a white line on the breast. 
The ev fence for discontinuous evolution lies in the manner 
in which these varieties are distributed among the multitude of 
brown whole-coloured rats. In some towns, rats were caught in 
such large numbers that it was possible to ascertain the constitu- 
tion of the rat population. It was found that the varieties occurred 
among the others in small groups, which were in some cases 
large enough to occupy two adjacent houses to the exclusion of 
other rats. The constitution and circumstances of some of these 
‘family groups ’’ was ascertained, but it was not possible to dis- 
cover the method of their origi It is an assumption to suppose 
