86 THE GROWTH OF GROUPS 



forehead star was found on two other occasions, in a 

 single sport caught at Poona and in four young ones 

 which were captured together in a trap at Calicut. 

 None of these were white bellied. The first mentioned 

 had a special peculiarity in possessing white feet, and in 

 the other four the extreme tip of the tail was white, but 

 this latter peculiarity is quite common among otherwise 

 normal rats. Thirdly, a sport was captured near Bombay 

 in which the last two inches of the tail were white ; a 

 similar, though not identically similar, character has been 

 used as a specific mark among various rodents and other 

 mammals. Fourthly, the peculiar general colour of the 

 couple was seen on several other occasions, but it is 

 perhaps less distinctive than the other three characters. 



These are reasons for believing that the four cha- 

 racters are independent things in the constitution of rats, 

 but how came it that all four were combined in both of 

 these peculiar individuals. The reason seems obvious. 

 They were of one line of descent in the narrowest sense, 

 being in all probability offspring of the same parents. 

 There is then evidence to show that these four characters 

 are appearing separately on many occasions in separate 

 places, but there is no evidence to show that the four 

 characters are appearing, in association, in separate 

 places. It may be said that the four characters which 

 are special to these two sports are not such as are used 

 by taxonomists to distinguish species. But it happens 

 that two of them have been used for this very purpose. 

 Thus albiventralism is characteristic of several defined 

 species of the rattus group which have certain other 

 special characters besides. Loss of pigment in the whole 

 circumference of tail in the terminal portion of its length 



