Revieics — ScJiarff's Origin of the European Fauna. 475 



Probable Date of the Separation of Ireland from England. — " If, 

 as I think, it may be taken as an established fact that the 

 south-western branch of the southern migration is the first, and 

 the Siberian migration the last, which reached the British Islands, 

 Ireland must have become disconnected from England during 

 the period intervening between the two. It was, therefoi-e, at 

 the time while the migration from Southern and Central Europe 

 was in progress, that the old land-connection uniting the two 

 countries was severed. That migration, however, did not stop 

 when the Siberian animals invaded Europe. Again, we find the 

 southern forms joining in with those of totally different origin 

 in their wanderings, just as the south-western fauna and flora 

 joined with the Central European. We still have confined to 

 South-Eastern England many of the latest immigrants from 

 Central Europe, such as Helix pomatia, H. carthtisiana, If. cantiana, 

 Baliminus montanus, and others. A large number of species of 

 plants might be mentioned, and also animals from almost all the 

 groups of terrestrial Invertebrates, which apparently had only 

 reached England before it became disconnected from Finance, and 

 which are still more or less confined to the south-eastern parts 

 of that country. The majority of these are of Central or South- 

 Eastern European origin. 



" Of the Invertebrates we have little or no palasontological proof 

 of the period of their migration to England. But with the 

 Mammals it is very different. We know that the vanguard of 

 the Siberian migration reached England at the time when the 

 Forest-bed was deposited. Every geologist is acquainted also 

 with the fact of the extraordinary mixture of Siberian and southern 

 types of Mammals contained in this bed, as well as in the 

 succeeding Pleistocene ones, and that it has been established beyond 

 a doubt that they must have then lived together, though their 

 original homes often were situated thousands of miles from one 

 another." (p. 486.) 



Influence of the Glacial Period on the Climate, and on the Fauna 

 and Flora. — " Whether the destruction of the fauna and flora was 

 caused by ice or water matters little. Almost all British geologists 

 and zoologists are agreed that the bulk of the Irish fauna and 

 flora migrated to Ireland after the Glacial period, because thej"^ are 

 somehow or other convinced that it must have been destroyed 

 had it reached the country before that period. I have mentioned 

 before that I do not share these views, and I have shown that 

 the range of species within the British Islands is incompatible 

 with the notion of a repopulation after the Glacial period. ' There 

 are few points,' says Professor J. Geikie, ' we can be more sure of 

 than this, that since the close of the Glacial epoch — since the 

 deposition of the clays with Arctic shells and the Saxicava sands — 

 there have been no great oscillations, but only a gradual ameliora- 

 tion of climate. It is quite impossible to believe that any warm 

 period could have intervened between the last Arctic and the 

 present temperate conditions, without leaving some notable evidence 



