142 EARTHWORMS AND THEIR ALLIES [ch. 



organs of the body which are more complicated else- 

 where. As one would expect with an archaic form 

 this genus is widely ranging, being found in all the 

 principal land masses of the globe except in the 

 Euro-Asiatic continent. 



Furthermore geographical facts would at least be 

 not contradictory to the view that this genus, and 

 therefore the terrestrial Oligochaeta generally, origin- 

 ated in the Antarctic hemisphere and that in pushing 

 northwards it has given off various descendants which 

 survive in the various regions of the world. Basing our 

 views of the possibilities of range among earthworms 

 on the actual facts already dealt with, it would seem 

 that the peopling of America from Africa or of Africa 

 from America, if it has occurred, has not taken place 

 through Europe and the north generally. For other- 

 wise we should expect traces of the passage. It is 

 true that we actually have Hormogaster as a possible 

 sign that the Geoscolecidae have passed this Avay. 

 But that is an isolated case and may be referred to 

 the extension northwards of this particular genus 

 rather than as an indication of a whole migration 

 through those territories. Another conclusion which 

 a collocation of the various facts brought together in 

 this book appears to lead to is that the group of the 

 terrestrial Oligochaeta is relatively speaking a modern 

 one. 



Convinced as we must be of the fact that range 



