232 



COLLEGE ZOOLOGY 



The classes of annelids are as follows: - 



(1) Class Archiannelida. -- Marine worms without setae or 

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

 Example: Polygordius (Fig. 162). 



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

 worms with setae and a perivisceral coelom ; often divided by 

 septa. Examples: Lumbricus (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 \ l-cc. 



pnp. 



FIG. 162. Polygordius appendicidatus. A, dorsal view. an, anus; 

 ct., cephalic tentacles; /z, 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.) 



