THE FAUNA OF BRITAIN. IOQ 



bridge? If any species came to that country in such 

 an unusual manner, surely they must have been Arctic 

 or northern forms. But what about the southern 

 species, which form the bulk of the Irish fauna and 

 also the flora? Even the Arctic element of the 

 British fauna, which probably includes, besides the 

 Reindeer, many hundreds of species, could not, I think, 

 have migrated to these islands on an ice-bridge. In- 

 deed, I agree with most of the writers who have dealt 

 with the subject, in asserting that the northern as well 

 as all the other elements of our fauna utilised for their 

 migration the old land-bridges which connected these 

 islands with one another and with the Continent. 



There is a greater diversity of opinion as to the age 

 during which the British fauna arrived in these islands. 

 This is naturally a much more complicated problem, 

 but it is one which I am convinced will ultimately be 

 solved mainly by means of a study of the geographical 

 distribution of animals and plants. I ft we can settle 

 the relative ages of the various migrations, wejhereby 

 supply afTTTTTpoTtant fink in our attempt to reconstruct 

 the past geographicallealures of the BritTsrTTslands. 

 The range ofthe~7Brttish species will give us ^rr 

 idea of the nature of the land-connections and their 

 gradual changes in course of time. Geological data 

 are exceedingly valuable in these inquiries, but it is 

 a fatal mistake to build our geographical theories 

 and the origin of the British fauna as a whole 

 entirely on the assumptions of a certain school of 

 geologists. Unfortunately, Dr. White's very interest- 



