The relationship between the palaearctic and nearctic faunas 285 



the theory, for instance Michaelsen (1922), Jaschnow (1925), Brehm (1926), 

 Herre (1935), and others; among botanists, Bocher (1938), Steffen (1941), Walter 

 (1954, p. 53 a.f.); vide also "Atlantisheft" (1939). In later years the critical voices 

 have been in the majority but some zoologists are still ardent supporters. Thus, 

 Modell (1943) thinks there is evidence for a Tertiary transatlantic connection in 

 Wegenerian sense from the fossil Mollusc fauna of Europe, but the facts brought 

 forth by him are quite in accordance with the late Tertiary European flora, as 

 investigated by Szafer (1954), which needs no such explanation (below, p. 310). 



His most loyal advocate among zoogeographers Wegener has found in Jeannel 

 who, in a long series of books and papers, the most comprehensive being that of 

 1942, has tried to explain any imaginable pattern of animal distribution as the 

 result of continental drift. 



Jeannel's method is not one of science, but of faith. He simply "believes" in 

 Wegener and, refusing to discuss any other explanation, makes "dogmatic state- 

 ments with no distinction between fact and opinion". The last citation is from 

 Darlington's excellent review (1949) of Jeannel's "Genese des Faunes Terrestres" 

 (1942), to which the interested reader is referred. 



Since, according to Wegener (1929, p. 20), the Atlantic was the ocean latest 

 formed and the continents bordering its northern part were the last to separate 

 (in Pliocene or even Pleistocene time), one would expect to find particularly clear 

 evidence of direct faunal exchange between Europe and North America, provided 

 the theory is true. But this is not so. 



As shown on preceding pages of this chapter, the number of Eur- American ani- 

 mal species lacking in Asia, which cannot easily be explained either by human 

 transport or as the result of dispersal across the Atlantic under conditions similar 

 to those of the present day, is so exceedingly small that any idea of general 

 contact between the European and American faunas in Pleistocene or Late Tertiary 

 time is sharply contradicted, other than through Asia and the present Bering 

 Strait. This has already been pointed out, in part, by 0kland (1927, pp. 361, 

 363) but, according to him, facts speak in favour of the "bridge theory". 

 Actually, not even the assumption of a late (Pleistocene), complete transatlantic 

 land-bridge, only of one joining Greenland and Iceland with the mainland of 

 Europe, seems to be a zoogeographical necessity. 



It must be frankly admitted that several single biogeographical facts would be 

 more easily understood by resorting to Wegener's theory of continental drift: i.e., 

 the distribution of the genera Hydromantes (p. 281) and Umbra (p. 281), of Cepaea 

 hortensis O. F. Miill. (p. 234 a.f.) and Tylos latreilli Ad. & Sav. (p. 280), provided, 

 in the latter cases, the idea of introduction has to be abandoned. But why should 

 the (superficially regarded) simpliest explanation always be the true one? Widely 



