THE GROWTH OF GROUPS 65 



in which some stacks of corn were yet standing. About 

 fifteen yards from these stacks ran a dyke separating the 

 field from the adjoining farm. In this dyke, which was 

 regularly honeycombed with them, the strange visitors 

 had taken up their abode. In less than an hour I counted 

 over forty of them running out and in from burrow to 

 stubble. Where they came from so suddenly, and in 

 such numbers, is a mystery to me, as I have been intimately 

 acquainted with the place for over thirty years, and a 

 black rat was never heard of in the locality, in fact the 

 country folk viewed them with serious apprehension of 

 some impending calamity.' " 



Messrs. Clarke and Hamilton then continue. " We 

 cannot offer any explanation of the above phenomenon, 

 but we may state that similar occurrences have been 

 reported from other localities. ... On the continent 

 of Europe the only instance of the occurrence of black 

 varieties of M. decumanm known to us is one recorded 

 by Milne Edwards (Ann. Sc. Nat. 1871), a large group of 

 black decumanus have been known in the menagerie of 

 the Museum." 



Groups of melanic rats, then, are not very rare. The 

 accounts of them, however, are likely to be disregarded, 

 because the attendant circumstances are, in most cases, 

 vaguely known. They produce wonder rather than 

 conviction. If in any place there is a firm local belief 

 that the rats of the locality are brown it will cause local 

 astonishment when a group of black ones appears in the 

 district, but the occurrence will not cause conviction in 

 one who has not the local belief. 



From a general point of view local hearsay is not to 

 be trusted. It should be noticed that in the case of the 



F 



