150 OLIGOCHAETA 



difficulties in the way of its transit across the sea, as there are apparently in the 

 case of other species If the species quoted in the above list had all been met with 

 in temperate regions, their wide range might possibly be accounted for by human 

 agency ; and even though they are not so met with, it seems to me very possible 

 that this is the reason for their being met with practically everywhere in the 

 tropics. Their non-occurrence in Europe is possibly a matter of climate. It 

 seems to me that the same arguments which I have used in order to prove that 

 the exotic species of Lumbricus are introduced appears to apply in the case of these 

 also. It is almost too remarkable in the case of Pontoscolex, for example, that the 

 examples from such widely separated regions of the earth as America, India, and 

 Australia, should belong to the same species. Now these species are always amongst 

 the most abundant in any gathering of worms from foreign parts ; this of itself 

 shows how great would be their chance of accidental transference as compared with 

 rarer species. But if this hypothesis be correct, how is it that other species, which 

 are equally common in their native countries, are not also found in the same 

 accidental way in other countries? For instance, Stuhlmannia variabilis, which is 

 undoubtedly one of the species most frequently met with on the east coast of Africa. 

 To this it is only possible to make the reply which, no doubt, largely begs the 

 question, that some species are more fit for living under different conditions than 

 others. It is a most remarkable fact about the Lumbricidae that they have the 

 capacity of establishing themselves anywhere, and, moreover, of largely ousting 

 the native inhabitants (a capacity, by-the-bye, which they share with their human 

 fellow-creatures of their native region). In gatherings of worms from cultivated 

 regions in New Zealand there were hardly any native species to be found ; the same 

 was the case with gatherings from the seaboard of South America. Prof. SPENCER 

 has informed me that in Melbourne to get native species it is necessary to go well 

 outside the town, the town gardens being filled with European species. 



In the following table is indicated the range of the genera of earthworms. 



1. Neotropical region (N). 



1. Geoscolex. 8. Tykonus. 15. LUMBRICUS, N 1 , P, 0, E, A 



2. Rhinodrilus. 9. EUDRILUS, E, 0, A. 16. PONTODRILUS, P, O. 



3. Anteus. 10. PERICHAETA, 0, A. 17. CRYPTODRILUS, 0, A. 



4. PONTOSCOLEX, 0, A. n. ACANTHODRILUS. E, A. 18. OCNERODRILUS, N 1 . 



5. Diachaeta. 12. Trigaster. 19. GORDIODRILUS, E. 



6. Onychochaeta. 13. BENHAMIA, E, 0, P. 20. Trichochaeta. 



7. Urobenus. 14. Kerria. 21. MICROSCOLEX, P, A. 



22. MONILIGASTER, O. 



