ScHARFF — On the Origin of the European Fauna. 479 



Glacial Period (inclusive of the period when the newer crags were 

 deposited) the White Sea remained connected with the Baltic and the 

 German Ocean, forming the great sea which I yentnred to call the North 

 European Sea (p. 462). Long before the Arctic migration reached 

 the British Islands, another migration advanced from the south ; first, 

 as I explained, from South -western Europe, and, as the climate became 

 colder, fi'om Southern and Central Europe. Many of the animals and 

 plants which arrived with the latter straggled northward into Scandi- 

 navia, and even at the present moment they seek to extend their 

 I'ange in a northerly direction. There is no evidence that their 

 progress was checked by the Arctic climate, which is supposed to have 

 prevailed during tlie Glacial Period; but this subject will be dealt 

 with more fully in the next chapter. As I have given a detailed 

 account of the nature of the southern migration in a paper recently 

 published in Prance (76 c), it will be found sufficient to merely repeat 

 the salient features, and add a few instances of distribution not 

 previously recorded. 



The Southern Migration. 



I have already mentioned (p. 429) that the bulk of the Irish fauna 

 and flora belongs to this migration, and that we can divide its members 

 again roughly into those of South-western and those of Southern or 

 Central European origin. But, in reality, the origin of this migration 

 is an exceedingly complex one, and is all the more difficult to trace, 

 as migrations from the south to the north have apparently proceeded 

 uninterruptedly during many of the past geological epochs — certainly 

 during the whole of the Tertiary Era. Whilst most of the larger and 

 short-lived forms have died out again, some of the less conspicuous 

 Invertebrates are undoubtedly of very ancient origin, and have 

 witnessed vast changes in the fauna and flora surrounding them. 

 ITany of these, though their general distribution indicates a southem 

 origin, baffle all attempts at solving the problem of the location 

 of their ancestral home. In some respects the southeni migration 

 merges into the Siberian one ; for there are a good many English species 

 of animals and plants which, though absent from Ireland, belong 

 certainly to the former. The dormouse {Muscardinus avellanarius), for 

 instance, is probably of Central European origin ; but it nevertheless 

 is absent from Ireland. Its general range, however, proves that it is 

 of very recent origin, and it has only spread from its original home, 

 which may be in the Alps, after Ireland was already disconnected 

 fi'om Great Britain. It has never reached Scotland, Spain, Korway, 



