vi PREFACE 



Since this volume mainly deals with the pheno- 

 mena of distribution, I have included in my survey 

 nearly all of the usually admitted genera of worms, 

 particularly of the terrestrial forms, which are in the 

 light of our present knowledge the more important 

 in considering this subject. 



F. E. B. 



Zoological Society of London. 

 December^ 1911. 



