232 



COLLEGE ZOOLOGY 



The classes of annelids are as follows: — 



(i) Class Archiannelida. — Marine worms without setae 01 

 parapodia. There is only one family, including two genera. 

 Example: Polygordius (Fig. 162). 



(2) Class Chaetopoda. — Marine, fresh-water, or terrestrial 

 worms with seta? and a perivisceral ccelom ; often divided by 

 septa. Examples: Liimbricus (Fig. 154), Nereis (Fig. 163). 



(3) Class Hirudinea. — Marine, fresh-water, or terrestrial 

 worms without setae or parapodia. Anterior and posterior 

 suckers are present. Examples: Hirudo (Fig. 169), Clepsine 



(Fig. 171)- 



3. Class I. Archiannelida 



A single family, Polygordiid^e, belongs to this class; it 

 includes two genera, Polygordius (Fig. 162, A) and Protodrilus. 



■e \hcc. ^r cf - 



k 



■M 



Fig. 162. — Polygordius appendiculatus. A, dorsal view. an, anus; 

 ct., cephalic tentacles; h, head. B, trochosphere larva, an, anus; e, eye-spot; 

 m., mouth. C and D, stages in development of trochosphere into the worm. 

 pnp, pronephridium. (From Bourne, after Fraipont.) 



