2l8 NATURAL HISTORY. 



by migrating hither at a time when Britain was not an 

 island, but was directly connected with other regions 

 by land. As regards the general or l Germanic ' flora, 

 there is no difficulty whatever in accepting this theory. 

 We have the most abundant evidence that at a geo- 

 logically very recent period (subsequent to the coming 

 into existence of our ordinary animals and plants), 

 Britain was directly connected with the continent of 

 Europe, the English Channel and the German Ocean 

 being in part or wholly converted into dry land. During 

 the same period of elevation, Ireland was united with 

 England, by the obliteration of the intervening sea. 

 It was, then, during the continuance of this land-con- 

 nection, that all our generally distributed plants and 

 animals migrated to our area from the Germanic regions 

 of the Continent. As this migration took place from 

 the east, the Germanic animals and plants necessarily 

 reached England at an earlier time than they found 

 their way to Ireland. We may further explain the 

 absence of certain common English plants and animals 

 (as, for example, snakes) from Ireland upon the sup- 

 position that the ultimate separation of Ireland from 

 England took place prior to the severance of the latter 

 country from the Continent. 



Modern geological researches also enable us to explain, 

 without any difficulty, the existence in the Highlands of 

 Scotland and the mountainous districts of the north of 

 England and of Wales, of plants peculiar to Scandinavia 

 or to the Arctic regions. We know, namely, that during 

 the glacial period, the greater part of our islands 

 participated in the frigid and Arctic conditions which 



