88 THE GROWTH OF GROUPS 



same character of caudal pigmentation as the species, but 

 this is not a proof that the character in the sports is 

 different in nature from a specific character, for we can 

 find another established species with a parti-coloured 

 tail in which the pigment is distributed in a manner 

 unlike that seen either in macleari or in the sports. Take, 

 for example, Mus blanfordi, which occurs among the hills 

 of Southern India. This species is closely allied to the 

 common rattus. Certain minor points have been de- 

 scribed as characteristic of its skull, but in specimens of 

 the species which are available for examination in the 

 Indian Museum, these points are not constant. M. 

 blanfordi is a white-bellied rat with white feet, its principal 

 mark of identification lies in the tail, which is white as 

 regards the terminal half in all its circumference. The 

 tail of blanfordi is peculiar, the tip being tufted with hair, 

 but if we overlook this additional character for the moment 

 and regard the pigmentation only, we shall see that it 

 is different from either of the others, for in this species 

 the colourless portion invades the coloured portion in an 

 irregular manner on all sides, so that small areas of pig- 

 mented scales are completely isolated from the main 

 pigmented area. 



Let us summarize the facts. 



(1) Two sports were found together, each possessed 

 the same four peculiar characters. All four characters 

 are known to occur separately in other sports. Therefore 

 they are not under any compulsion to appear in associa- 

 tion with one another. 



(2) The fact that all four appear together in a single 

 individual sport may therefore be spoken of as accidental, 

 the cause being unknown. But the fact that all four 



