48 THE GROWTH OF GROUPS 



of the tail in the terminal portion of its length. This 

 is seen in a species which occurs in the hills of Madras 

 (M. Uanfordi), and also in other species outside India; 

 In Uanfordi the caudal albinism is accompanied by a 

 considerable lengthening of the hair of the tail so that it 

 forms a terminal brush-like tuft. Rats showing this 

 particular type of caudal albinism were found near 

 Amritzar in the Punjab and near Bombay. In those 

 from the former place there is no lengthening of the 

 caudal hair, while in that from the latter place this pecu- 

 liarity is well marked. It is almost certain that these 

 peculiar rats were not part of an established species, but 

 belonged to a limited family group ; in the case at Am- 

 ritzar this was satisfactorily proved, as will be explained 

 later on. 



Another type may be mentioned in which the tip of 

 the tail is white. This is found in rats of various species. 

 Sometimes it is common among rats caught in a particular 

 area. 



(4) The breast stripe. Rats are occasionally found 

 which differ from the normal whole-coloured ones in 

 possessing a short white line in the middle of the breast 

 between the forelegs. There is another kind of breast 

 stripe which in a sense is the converse of the last mentioned, 

 some white-bellied rats have a median coloured stripe in 

 the same position. 



(5) The forehead star. This peculiarity, well known 

 among mammals, has not been used, to my knowledge, 

 as a specific mark in the genus Mus. It was found 

 on three occasions among house rats in India, in a 

 mature pair caught together in the Amritzar district, 

 in a group of four which were caught together in 



