64 HISTORY OF THE EUROPEAN FAUNA. 



Siberian fauna set foot in England, since it has been 

 shown that a continuous land-surface was necessary 

 for their migration. Owing to the perfect preserva- 

 tion of the remains of the Siberian migrants in recent 

 continental deposits, the history of that migration 

 can be clearly followed, and it is possible even to 

 determine the date of its arrival in England in 

 geological language at any rate. The time of the 

 colonisation of Ireland can be thus approximately 

 fixed as having taken place at a period prior to the 

 arrival of the Siberian migrants in England. 



All those who have seriously studied the problems 

 presented by our British fauna notably the late 

 Professor Forbes, and more recently Mr. Carpenter 

 and myself are agreed that the Lusitanian element 

 is the oldest, and that the newest is that which has 

 come to us from the east. 



The sequence of events in the British Islands was 

 probably as follows : The first comers were the 

 members of that fauna which issued from South- 

 western Europe; then came the Alpine, and at the 

 same time probably the Arctic and the Oriental; 

 and finally the Eastern or Siberian. The migrations 

 of all but the last continued, uninterruptedly, for very 

 long periods. 



The study of these migrations has convinced me 

 that, though climate was a powerful factor in the 

 evolution or history of the European fauna, the 

 geographical changes which took place on our con- 

 tinent in later Tertiary times exerted a yet stronger 



