CH. Ill] EXTRA-EUROPEAN LUMBRICID^. 153 



rather to indicate that it is modern. Indeed the world- 

 wide distribution of the three genera is really in all 

 probability due to the interference of man and not to 

 their own unaided efforts. The reasons for this are 

 twofold. In the first place it is important to show that 

 accidental transference is possible. This is shown by the 

 fact that Wardian cases received at the Royal Gardens 

 Kew frequently contain earthworms which have been 

 included accidentally. 



In plenty of other ways could specimens be conveyed 

 in this way from one country to another. Now were the 

 occurrence of the same genera in so many and so distantly 

 separated parts of the world a fact due to natural causes 

 alone, we should expect to find some differentiation of 

 species. But this is precisely what we do not find. 

 Without a single exception 1 the Lumbricidae from extra- 

 European regions are identical with those of Europe ; 

 there is not even a variety known which is characteristic 

 of a foreign continent. This is an argument of great 

 force ; if this dispersal were of old standing, as it must 

 have been were it brought about by purely natural causes, 

 time would have elapsed to allow of some modification in 

 various directions. The second argument is derived from 

 a consideration of the actual range of the presumably 

 imported species in the country of their adoption. Dr 

 Michaelsen has pointed out that in South America, where 

 Lumbricida3 are very abundant, they are most abundant 

 in cultivated ground near to the coast, nearest to the point 



1 Unless Allolobophora Japonica. But of course Japan belongs to 

 the Palaearctic region. 



