734 RODENTIA—RATTUS 
. 
1. Rattus rattus. 
Since the account, at p. 592, of the Geographical Variation of this 
species was published, the house rats of India, Burma, and Ceylon have 
been studied by Hinton (/. Bombay NV.H.S., 28, pp. 59-88, 384-416, 716- 
725, 906-918, 1918 and 1919). This work was based upon the rich 
material gathered during the mammal survey of India, undertaken by 
the Bombay Natural History Society, as well as upon the collection in 
the British Museum. In the various Mammal Survey Reports published 
by Wroughton and others in the /ournal cited, the Indian house rats 
were listed as “ Hpzmys rufescens” when they had dusky bellies, and as 
“ Epimys rufescens, var.” when their under parts were white. That this 
difference in colour had some geographical value had long been 
apparent; and it was thought that the white-bellied and dark-bellied 
types might belong to two distinct sub-species or even species. To 
test this possibility was one of the chief objects of Hinton’s work. The 
results arrived at may be briefly summarised as follows :— 
The common Indian house rats, whatever may be their colour, 
are all referable to XR. rvattus; but the forms described as R. xztedus 
Hodgson, and &. vicerex Bonhote, about the status of which there has 
been controversy, are distinct species of the 2. vatéus group. 
Like their European representative R. 7. frugivorus in the Medi- 
terranean region, the Indian white-bellied forms of A. rattus (“ Epemys 
rufescens, var.” of the Survey Reports) are essentially wild animals, often 
living out of doors in jungle and woodland in the most remote rural 
districts of India, Burma, and Ceylon. As wild mammals they show 
a definite geographical variation, so that many sub-species have now 
to be recognised. Descriptions of these are given in Hinton’s paper. 
With regard to the dark-bellied Indian house rats the case is 
different. Wroughton (/ournal cited 28, p. 474) had already put 
forward the view that the white-bellied forms of A. va¢tus in the Indian 
region represent the primitive wild form of the species, while the dark- 
bellied types have developed from these wild forms in response to 
changes of environment which have ensued upon the species becoming 
partly or wholly commensal with man,—the darkening of the under 
parts in the least modified of the Indian races, no less than the 
darkening of the back in the wholly parasitic R. ~ rattus, being 
the outward indication of domesticity. These dark-bellied forms 
(“ . rufescens” of the Survey Reports) are in great measure restricted 
to the districts of India which possess substantial houses; and they 
are far less frequently caught out of doors than are the white-bellied 
races. Series of dark-bellied specimens from single localities or 
colonies are frequently very uniform in appearance and structure 
among themselves; but when series from different, though sometimes 
neighbouring localities are examined, an enormous range of variation 

