ANNELIDA 



295 



Protodrilus . As in Polygordius but with segmentation marked ex- 

 ternally by ciliated rings and with a longitudinal cihated groove in the 

 middle of the ventral surface ; with a ventral muscular pharyngeal sac ; 

 hermaphrodite. 



,ten. 



Fig. 204. Examples of the Archiannelida. A, Nertlla, dorsal view of female: 

 A', parapodium. B, Saccocirrus, side view of anterior end. C, Histriobdella, 

 dorsal view of male. D, Dinophilus, dorsal view of male. amp. ampulla of ten- 

 tacle {ten.)\ a.f. anterior foot; ch. bundle of chaetae; cl. clasper; cil.b. bands 

 of cilia ; e. eye ; gen.s. genital segment ;]. jaw ; /. eyes ; nep. nephridia ; o. ovary ; 

 od. oviduct ; p. penis ; ph. pharynx ; p.f. posterior foot ; p.p. palp ; rm. rectum ; 

 St. stomach; v.s. vesicula seminalis; f.. testis. A, B, after Goodrich; C, after 

 Shearer; D, after Harmer. 



A single species, P. chaetifer^ has recently been discovered with four 

 short chaetae in each segment. 



Saccocirrus (Fig. 204 B). As in ProtodriluSy but with chaetae 



