130 HISTORY OF THE EUROPEAN FAUNA. 



phenomena of the country can therefore be inter- 

 preted in different ways, even by those who are 

 convinced that they are due to land-ice and not to 

 icebergs or mud-glaciers. 



SUMMARY OF CHAPTER III. 



The history of the British fauna is not only of interest to us 

 from a sentimental point of view, it is a convenient starting- 

 point in the study of the larger European problem. The fauna, 

 broadly speaking, is composed of three foreign elements, viz., the 

 northern, eastern, and southern, to which may be added a small 

 endemic one. Examples are given of the more noteworthy forms 

 belonging to each of these. This leads us to the subject of the 

 natural divisions of the British Islands according to their animal 

 inhabitants. Zoologists attempted at first to subdivide these 

 countries, on the lines laid down by botanists, into a large 

 number of provinces. Forbes proposed ten such divisions for 

 mollusca, and subsequently five, which were ultimately reduced 

 by others to two or three. 



The opinions of biologists are almost unanimous in attributing 

 the bulk of the British fauna and flora to migrations by land 

 from the Continent, but two other theories, viz., those of Pro- 

 fessor Cole and Messrs. Kinahan and Lamplugh, are also 

 referred to. The first believes in a possible migration eastward 

 from Western Europe, and the latter support the view of the 

 former existence of ice-bridges to assist the fauna in their 

 migrations. 



An endeavour is next made to determine at what geological 

 periods the various migrations entered the British Islands. 

 There is considerable difference of opinion on this subject. 

 Some believe that the British fauna is altogether post-glacial ; 

 a few think that it is partly so and the remainder glacial ; 



