90 HISTORY OF THE EUROPEAN FAUNA. 



eastern migrations insensibly merge into one another, 

 so that it is often very difficult to determine to which 

 of them an animal may belong. The European 

 species spread principally from three centres over 

 Europe viz., from the Lusitanian, Alpine, and the 

 Balkan centres. The southern element of the British 

 fauna is therefore composed of animals which have 

 originated in these three centres, and in Central and 

 Southern Asia. The Balkan species have been 

 included with those coming from the latter centre 

 under the term "Oriental" migration. The sixth 

 chapter is devoted to it, whilst the Lusitanian and 

 Alpine migrations have each a chapter to them- 

 selves. 



The Arctic Hare is, as I have already mentioned, 

 one of the mammals of the northern element of the 

 British fauna. It is now confined to the mountains of 

 Scotland and the plain and mountains of Ireland. 

 But in former times it had a wider range in the 

 British Islands. The Stoat is another distinctly 

 northern mammal. It occurs with us, as Messrs. 

 Thomas and Barrett-Hamilton have pointed out, 

 in two distinct varieties or species, the one being 

 confined to Great Britain, the other to Ireland. As 

 I shall explain more fully later on (p. 135), I have 

 reasons to believe that the Irish Stoat came from the 

 Arctic Regions as a northern migrant, but that the 

 English Stoat, on the other hand, reached England 

 with the Siberian fauna from the east. A third 

 northern animal, now extinct in the British Islands, 



