X 



PHYLUM ANNUL A.TA 



483 



In adult structure, particularly in the absence of parapodia and 

 setie and of a ccelome, the Hirudinea diverge somewhat widely 

 from the Chsetopoda ; but a study of their earlier developmental 

 stages shows unmistakably their close connection with the latter 

 group, more particularly with the Oligochasta. 



The following diagram will serve to illustrate this view of the 

 relationships of the various groups referred to : 



Polychaeta 



My i o sl'otnida 



Cefihyrea 



Oligochael'a 



Hirudinea 



Archi-Annelida 



Dinofjhilea Roh'Fera 



-Gaslrolricha 



Tr ocho (shore 



Fit.;. 3S5 Diagram illustrating the relationships of the Annulata and the Trochclminthes. 



I I 2 



