150 



p. OMODEO 



they differ significantly both in morphology and in degree of ploidy (cf. 

 Omodeo, 1957). 



In my opinion, the sum of these arguments points to only one explanation 

 for the type of distribution we are dealing with, the existence of a land-bridge 



Fig. 15. Distribution of Dertdrobaena octaedra and Spaiganophilus. 



across the North Atlantic along which the earthworm fauna of Europe moved 

 to North America, and a few rare American species went in the opposite 

 direction, in a relatively ancient age, but not so ancient as to permit specific 

 differentiation of most of the Lumbricidae. 



REFERENCES 



Cernosvitov, I. (1936). Notes sur la distribution mondiale de quelques Oligochetes. 



Mem. Soc. Zool. Tchechosl. 3. 16-19. 

 Darlington, P. J. (1957). Zoogeogiaphv. New York. 



Gates, G. E. (1929). Earthworms of North America. /. Wash. Acad. Sci. 19, 339-347. 

 Gates, G. E. (1952). New species of earthworms from Arnold Arboretum, Boston. Breviora 



Mas. Conip. Zool. Cainhr. 9, 1-3. 

 Gates, G. E. (1957). Contribution to a revision of the earthworm family Ocnerodrilinae. 



The genus Nematogenia. Bid/. Miis. Comp. Zool. Caiiihr. 117, 427-445. 

 Joleaud, L. (1939). Atlas de paleobiogeographie. Paris. 

 Lindroth, C. H. (1957). The Faimal Connections between Europe and North Anierica. 



Stockholm. 

 Matthew, W. D. (1915). Climate and evolution. Ann. N. Y. Acad. Sci. 24, 171 318. 



