88 Records of the Indian Museum. [Voi.. Ill, 



and Mus; in these, however, the occurrence is not associated with 

 lengthening of the terminal hair. 



Case 4. — One half-grown rat selected from some thousands of the 

 mixed assembly of white-bellied rattus and concolor caught in 

 Rangoon city, which differs in onl}- one respect from man}^ of the 

 half-grown members of the white-bellied race. The under side 

 of the tail of this rat is pure white. This is considered to be a most 

 important variation, for on this peculiarity^ alone several species 

 have been defined. This statement is open to criticism, but it 

 cannot be denied that bicoloration of the tail is the most important 

 feature in the definitions of those species of the genus Mus which 

 have received the names of niveiventer, vicercx, bukit, rapit, etc., 

 for the other less important details of the definition of these species 

 seem to fall within the normal range of variability of the Mus 

 rattus group, and the species have been defined from comparatively 

 small numbers of specimens. 



The fact that this young rat was only half grown is of im- 

 portance ; judging from its size it cannot be much more than two 

 or three months old ; this lessens the probability^ of its being brought 

 to Rangoon by a foreign ship. Because of this and of the fact 

 that it appeared to be unique among the large number examined, 

 it is difficult to believe otherwise than that it was a sport, born of 

 the white-bellied race of Mus rattus which is common in Rangoon. 

 In case 8 we shall see another example of precisely this same varia- 

 tion, occurring in a group of rats found to be occupying two ad- 

 jacent houses in Naini Tal. 



Cases of more than one individual showing the same 



variation as sports which have been met at 



the same time and Place. 



Case 5. — An excellent example of this is from the Punjab. 

 Captain Davys sent us from a village in the Amritsar district a 

 pair of adult rats of almost exactly the same size and appearance. 

 They are obviously of the rattus type, but can be distinguished at a 

 glance from the others of that race among which they were found. 

 They are much lighter in colour than the average Punjab rattus, 

 though not lighter than certain exceptional individuals. They 

 both have a pure white star on the forehead ; the terminal third of 

 their tails is white. The sender of these remarkable rats allu- 

 ded to them tentatively as Mus brahminicus. There is very 

 little doubt that if they had been sent together to any specialist, 

 they would have been hailed as a new species. However, cir- 

 cumstances make it probable that in the capture of these two 

 specimens, the new species would have become extinct before it 

 was defined. They were almost certainly born of the same parents 

 and were probably mates. The female was pregnant, carrying four 

 embryos. They were caught in the village of Nowshera Dhala,. 

 in which over 800 of the normal Mus rattus had been taken. These 



