142 p. OMODEO 



Malayan peninsula; the African species Eudrihis eugeniae, dispersed volun- 

 tarily and involuntarily by man, colonizes much of the United States, where- 

 as its original environment is the equatorial forest. Such an extraordinary 

 adaptability makes it hard to imagine a climatic modification capable of totally 

 destroying the populations of a genus or a family of earthworms living on a 

 continent: it is almost certain, as we shall see, that the Lumbricidae of Green- 

 land and Iceland have survived in situ all of the Last Glacial and maybe the 

 entire Quaternary. 



The competition among these saprophagous species is very slight: in an 

 area of a few square meters, in Africa as well as in Europe, it is possible to 

 collect individuals belonging to 15-20 different species and also to two or 

 more families. In any Tuscan garden it is normal to find living together 

 species of Lumbricidae, Microchaetidae and Acanthodrihdae (the latter 

 introduced). This being the situation, the substitution of an entire family of 

 earthworms by another over a whole continent does not appear probable. In 

 this connection, I think it is worth while to recall the case of the family 

 Phreorictidae (or Haplotaxidae) — certainly very ancient and primitive and 

 probably the ancestor of all living families of earthworms — containing 

 endemic species belonging to two or three genera in all corners of the world : 

 from Europe to New Zealand, from Sumatra to Japan, from the Cape to 

 Guinea. In colder climates these species take shelter in phreatic waters, in 

 hotter climates they occupy surface as well as subterranean waters; in any 

 case they always have been found wherever an accurate investigation of the 

 fauna has been carried out. 



Summing up. we can say that although Matthew's (1915) theory appears 

 plausible for an explanation of the discontinuity of the neotropical Acantho- 

 drilinae or the absence of the Octochaetinae in equatorial Africa, it is com- 

 pletely inadequate to justify the principal pattern of earthworm zoogeography. 



It remains to consider the theories that suggest major modifications of 

 the continental areas and of their reciprocal relationship through the geo- 

 logical eras: the theory of the intercontinental land bridges, and that of 

 continental drift. 



Only geophysicists and geologists can decide which of the two theories is 

 correct or at least preferable; however, while waiting for them to come to an 

 agreement on this point, I shall state my point of view. 



Personally I prefer a certain eclecticism and would tend to explain the 

 genesis of the earthworm fauna of the central and southern countries facing 

 each other on both sides of the Atlantic Ocean on the basis of Wegener's 

 theory and the genesis of the fauna of the North Atlantic countries on the 

 basis of the land-bridge theory. 



A glance at the present distribution of earthworms superimposed on 

 Wegener's paleogeographic maps (maps, Figs. 8-10) is more satisfactory 

 than a long discussion. It demonstrates how simply and completely can be 



