ix] GEOGRAPHICAL DISTRIBUTION 129 



CHAPTER IX 



THE GEOGRAPHICAL DISTRIBUTION OF 

 EARTHWORMS 



The facts referred to and considered in the last 

 chapter lead to further observations upon the geo- 

 graphical distribution of this group of animals and 

 suggest problems for solution. 



It is not the place here to give a general sketch of 

 the division of Biology termed Zoogeography ; but a 

 few general conclusions must be laid before the reader 

 in order to render what follows intelligible. It is 

 universally agreed that the range in space (and in 

 time also) of a given species of animal (or plant) is 

 as much a part of its scientific definition as are its 

 anatomical characters. A description for instance of 

 Acanthodrilus migulatus is incomplete without a 

 reference to the fact that it occurs in, and is confined 

 to, the island of New Caledonia. 



Each continent or island or part of a continent 

 and part of an island has its own peculiar inhabitants 

 as well as some others which range beyond its confines. 

 Thus as we have seen the genus Hyperiodrilus is 

 confined to the tropical West of Africa while the 

 genus Dichogaster also found in that region is also 

 met with in other parts of Africa as well as in certain 



B. E. 9 



