PRELIMINARY CONSIDERATIONS. 8/ 



SUMMARY OF CHAPTER II. 



I have endeavoured to show in this chapter how we can deter- 

 mine approximately the original home of an animal. By this 

 means we are able to study the component elements of the 

 European fauna, which is found to consist to a large extent of 

 migrants from the neighbouring continents. There is a Siberian, 

 an Oriental, and an Arctic element in it. The remainder of the 

 fauna is derived from local centres of dispersal. "What was 

 formerly believed to have been one great northern migration 

 now resolves itself, on closer study, into two very distinct 

 ones the Siberian and the Arctic. The mammals have 

 received most attention hitherto, because their remains are so 

 frequently met with, thus enabling us more easily to investigate 

 their past history; but butterflies and snails have not been 

 neglected, and at least one very remarkable work on the latter 

 has been published dealing with their origin in Europe and 

 in the remainder of the Palsearctic region. 



The former distribution of land and water is intimately con* 

 nected with the origin of the European fauna, and the changes 

 which have taken place in this respect may be best traced by 

 the present distribution of mammals, snails, and earthworms. 

 In this manner the British Islands may be shown to have been 

 connected with one another and with the Continent; Spain 

 with Morocco across the Straits of Gibraltar; Greece with Asia 

 Minor, and so forth. 



The British fauna has played such an important part in the 

 evolution of the European fauna, that it forms the key to the 

 solution of the wider problem. In it five elements are 

 recognisable, of which the Lusitanian element is the oldest, 

 and the Siberian the most recent. It has been deemed 

 advisable to conclude this chapter with a short review of the 



