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CHAPTER III 



chamissonis Fisch. {groenlandicus Dej.), a beetle now restricted to arctic-subarctic 

 North America (the record for Greenland being erroneous). Since the elytral 

 sculpture is very characteristic in this species, a wrong identification seems out 

 of the question.— For a review of the late Tertiary and Pleistocene fossil insects of 

 Europe, vide Henriksen (1933, p. 265 a.f.). 



The key to a proper understanding of the now extinct American element, not 

 only of the European flora but also of the contemporaneous/awna, seems to be given 

 by the balance between American and East Asian plants in the different periods 

 investigated by Szafer (diagr. 11). Until, and inclusive of, the first part of the 

 Giinz-Mindel Interglacial the curves for these tzvo elements run perfectly parallel, 

 the East Asian element being clearly in the majority. This is definitely not what 

 could be expected if the presence of the American plants was due to a Transatlantic 

 land-connection. In that case, the American element would have increased at 

 the cost of the East Asian. The parallel development of the said elements can only 

 be explained under the assumption that the "American'' plants were simply part of 

 the East Asian group, that they invaded Europe together from the east. 



The longer persistence in Europe of some few members of the American type 

 {Duiichium, Osmunda, Sec.) does not contradict this opinion, because it must be 

 expected that these plants, being able to reach both Europe and eastern North 

 America from a centre in Asia, belonged to the most hardy and most easily dis- 

 persed plants of the group which, in full, ought to be called "East Asian". The 

 only obscure point is why they later, entirely or in part, became extinct in Asia. 



The opinion here stressed, that northeastern Asia has served as an evolution 

 centre for circumpolar animals, is quite in accordance with Hulten's view (1937) 

 of the development of the Holarctic flora. But to my mind, Huhen has underesti- 

 mated, (a) the possibility of transatlantic dispersal without the aid of land-connec- 

 tions, and (b) the importance of an element of original (endemic) species in Europe 

 and North America. Then it is evident that the mountains of both regions possess 

 a rich element of indigenous species though, for some reason, these have almost 

 failed to spread outside their area of origin. 



The reasons may be tentatively indicated as follows: —The main areas of specia- 

 tion were mountains. They possess a great variety of habitats and the strong short- 

 way zonation shapes small isolated population areas, thereby favouring speciation. 

 The Tertiary mountain ranges, the Alps, the North American Cordilleras, &c., 

 are young. They have existed long enough to allow for speciation but not for the 

 development of really new "inventions", higher taxonomic units, essentially new 



