THE GROWTH OF GROUPS 59 



which were captured were all mature or nearly so. Rats 

 breed all the year round, producing about four genera- 

 tions in that time. Consequently we may be sure that 

 there were a number of young ones of various ages re- 

 maining in the houses. 



We have now arrived at the following conclusion. 

 There were living at the time of the inquiry (1908) in 

 two adjoining houses at Rangoon, a considerable number 

 of rats possessing certain special characters by which 

 they could be recognized unmistakably from other rats ; 

 that is to say, as a group they fulfilled the conditions 

 which are commonly required of a " species," and it is 

 highly probable that if four or five of them had been 

 sent together to a museum they would have been regarded 

 as a new species or variety. Indeed this group has a 

 better claim to be commemorated by a name than some 

 of the species which have been denned in recent years. 



The special characters common to the members of this 

 group, are as follows. In the first place, melanism. By 

 this peculiarity alone they could be distinguished at a 

 glance from the common mole-rats, which are greyish 

 brown. The two kinds appear strikingly different even 

 at a distance of several yards. The group was melanic 

 in the strictest sense, not a brown hair was visible in 

 any of them. Black and slatey blue were the only colours 

 appreciable. 



If it had not been for their colour, doubtless their 

 other peculiarities would have been overlooked, since 

 they are less noticeable, being, so to speak, within the 

 range of variability of the species (i.e. of the estab- 

 lished or parent species). These peculiarities are as 

 follows. The skull is narrower and the nasal bones are 



