88 EARTHWORMS AND THEIR ALLIES [CH. 



them some 58 species ; eight of the genera are 

 peculiar to the islands. 



From this brief statement of facts some inferences 

 of interest can be drawn. It is in the first place plain 

 that every part of the world except the extreme north 

 and south has a considerable fauna of earthworms. The 

 one exception would appear to be the northern part of 

 the North American continent. Here we meet with 

 members of the family Lumbricidae which are however 

 species that are met with in the Euro-Asiatic province 

 and are thus to be regarded as possibly later immi- 

 grants introduced probably by man. Thus temperature 

 short of a constantly frozen condition of the ground 

 is not a bar to the existence of earthworms. Even a 

 freezing of the ground for lengthy periods is not 

 a complete obstacle to the existence of those Annelids ; 

 for I have myself received examples of Lumbricidae 

 from the arctic island of Kolguev. Moreover the 

 temperate regions would seem to be as fully popu- 

 lated in the way of individuals, and even of species, 

 as are the tropical regions. Indeed as to individuals 

 it seems that the temperate regions are more fully 

 supplied than much of the tropics. This however is 

 not quite the object of the present section to discuss. 

 We are here concerned with the relative frequency 

 of genera and species. There are according to a 

 recent estimate of the Rev. H. Friend some forty 

 species recognisable in Great Britain. And as already 



