1909.] R. E. LivOYD : The Races of Indian Rats. 3 



is some evidence that this is so in the case of Madras cit3^ The 

 distribution of the several species of common rats varies consider- 

 ably throughout India ; especially is this true of the principal 

 sea-port towns. Dr. W. C. Hossack's investigation has shown 

 that the rats of Calcutta city are surprisingly different from the rats 

 of Bombay, which have been described in the reports of the 

 Plague Commission. It will be shown that the rats of Rangoon 

 and Madras cities are also different both from one another and 

 from those of Calcutta and Bombay. 



PREVIOUS WORK ON INDIAN RATS. 



At the outset it must be pointed out that these results have 

 followed directly on Dr. Hossack's investigation of the rats of Cal- 

 cutta [i], and are in direct continuation of that work, to the author 

 of which every acknowledgment is due, not only for the guidance 

 afforded by the work itself but also for the results of his experience 

 conveyed in a personal manner. 



In an ' historical ' paragraph Dr. Hossack reviews the previous 

 writings on the subject of Oriental rats, and although it is un- 

 necessary to repeat that statement here, it may be again 

 mentioned that Mr. Thomas's paper [2], published in 1881, is the 

 foundation on which any subsequent work on the subject must 

 be built. The account of the rats in the Fauna of British India 

 seems to have originated from this source. 



As these observations are in continuation of Dr. Hossack's 

 work, it does not seem necessary to again define the common 

 Indian species of rats ; it will be sufficient to say that they support 

 the opinion that Mus rattus, the common rat of India, is, in colour 

 and quality of fur, a most variable species, and that its variations 

 are so numerous and seem to occur in such perfect gradation, 

 when large numbers of specimens are examined, that definite 

 varieties can rarely be established. It will be shown, however, 

 that even in its range of variability Mus rattus is not constant 

 throughout India. In some places there is a tendency for rats of 

 this species to breed true to some particular type, while in others 

 they exhibit a range of colour-variation as wide as that of the 

 species in Calcutta (Hossack [i, pages 17 and 18]). 



To name new varieties of the species seems unwise, for there 

 is nothing to show that the rats which breed true to some 

 particular type in a given district at the present day were in the 

 same state fifty years ago, or will be found in a like condition 

 fifty years hence. It must be remembered that one hundred 

 generations of rats pass within the lifetime of one man. More- 

 over the following objection to the naming of varieties may be 

 framed: — To establish a variety and lay down one specimen as its 

 "type" is to acknowledge tacitly that all animals subsequently 

 found from far and near which closely resemble that type must 

 be genetically related to it. After examining large numbers of 

 animals taken from widely separate localities, doubts arise as 



