470 Proceedings of the Royal Irish Academy. 



wMch would have impeded their journey. In Scandinavia, Arctic 

 animals and plants form a large proportion of the fauna and flora, and 

 as we proceed northward, southern forms hecome more and more 

 scarce. According to Mr. Peterson, no less than thirteen species of 

 Arctic Lepidoptera occur in Northern Europe and North America, but 

 are absent from Asia, and he assumes the probability of a direct land 

 connexion between the two countries by way of Greenland before 

 the Glacial Period, and a survival of these in Eujope (67, p. 57). 



My assumption that the Arctic element of tiie fauna and flora, 

 which undoubtedly exists in the British Islands, and which is now 

 confined more or less to the northern parts of Great Britain and Ire- 

 land, niigi-ated by a direct route from Scandinnvia, is not founded on 

 geological data alone, but has been suggested to me in a great measure 

 by the present range of the Arctic species. Let us take some examples. 

 I have referred to three species of Mammals, viz. tl'e hare {Lepus 

 variabilis), the stoat {Miistela erminea), and the reindeer {Rangifer 

 tarandiis), which I suppose to huve migrated to Ireland diiectly from 

 the north, or more correctly the north-east, and it is essential that I 

 should dwell on the history of each of these for a little, as their past 

 range is so much better known than any of tlie other members of the 

 Arctic migration which we have to deal with. 



Lepus variahilis. — To those who are not acquainted with the fact, 

 I may mention that this hare is the only one inhabiting Ireland, and 

 that it lives in tlie plain as well as in the mountains. In Great 

 Britain it is confined to the mountains of Scotland, wliil^t the plain 

 is inhabited by the European hare {Lepxis europceus), which, I have 

 shown, came originally from Siberia. L. variahilis is found on such 

 widely separated mountains as the Pyrenees, Alps, Tatra, Caucasus, 

 and the Akita and Mioko-san mountains in Japan, whilst quite absent 

 from the plains surrounding them. It is perfectly clear that at some 

 time or other it must have inhabited these plains, but it has since 

 disappeared from them, thus producing discontinuous distribution, 

 wliich, as I have already stated, is a proof of antiquity. Besides, 

 the vastness of the range alone indicates this, and its migration south- 

 ward must have taken place at a very remote period. On the 

 continent of Asia and North America it is confined to the northern 

 parts. In Northern Europe we find it in Scandinavia, and almost 

 everywhere in the Arctic regions. Its home is therefore in the north ; 

 During the Glacial Period it is supposed to have been driven south, 

 and its occurrence in the Caucasus, the Alps, and the Pyrenees is 

 looked upon as a standing testimony to the extreme refrigeration of 



