428 ANIMALS INTRODUCED UNAWARES 



Kincardine), but in this country the Black Rat has never been 

 able to face the competition of the Brown, and disappears 

 as certainly and almost as rapidly as it comes. Yet in the 

 days of its abundance the influence of the Black Rat was 

 more important than mere numbers would suggest, for, as 

 I shall discuss in another place, its presence was a pre- 

 dominant factor in the occurrence and distribution of the 

 plague which ever and again ravaged the great cities. 



THE ALEXANDRINE RAT 



Closely related to the Black Rat, indeed usually regarded 

 as a brown-coloured tropical race of the dark species, the 

 Alexandrine Rat (Afus (Epimys] rattus alexandrinus] ranges 

 from south-eastern Europe and northern Africa to India. 

 It has long been known to pay passing calls at our ports, 

 on board ships from the East, and Dr Eagle Clarke and 

 Mr William Evans have recorded many specimens from 

 steamers in Leith. Yet it seems never to succeed in 

 establishing colonies, though recently specimens have been 

 found in company with the Common Rat in the stores of 

 the Zoological Park at Corstorphine near Edinburgh. 

 Whether the two species will succeed in living there in 

 harmony, in view of the abundance of the food supply, is a 

 matter which only years, or the ratcatcher, will settle. 



THE COMMON OR BROWN RAT 



Most successful of the stowaways has been the Common 

 or Brown Rat {Mus (^Epimys} norvegicus), which from its 

 native home on the steppes of Asia, in the regions which 

 lie between Lake Baikal and the Caspian Sea, has spread 

 from country to country till the whole of the civilized world 

 has become its playground. Romance of a sort attaches to 

 the story of the colonization of Europe by the Brown Rat, 

 partly because of its extraordinary success. We cannot but 

 wonder at the first hordes of the invading army, which in 

 1727, Pallas tells us, compelled by the dearth caused by an 

 abnormal year of multiplication in their native territory, 

 burst their bounds and like a living river, flowed westwards 

 from the Caspian region across the Volga, whose bed was 

 choked with their dead bodies, and away to the west and 



