34 EARTHWORMS AND LEECHES [CH. I 



Family NAIDID^E. Septa developed. Brain separated from hypo- 

 dermis. Asexual reproduction frequent. Setae in two or 

 four groups per segment. Ventral setae prong-forked and 

 hooked : dorsal various. Testes in segments 5th or 7th, 

 rarely in 8th and 9th : ovaries in 6th or 8th, rarely in 10th. 

 Spermatheca in 5th or 7th. 



genus Paranais Czern. Two dorsal and two ventral groups of 

 setae per segment. Segment 3 not longer than the rest. 

 Dorsal and ventral setae prong-forked and hooked. Testes in 

 8th and 9th, ovaries in 10th. 



P. litoralis (Mull.) Orst. First dorsal setae on segment 5 : longer 

 and more slender than ventral setae. Margins of fresh and 

 brackish water. 



genus Chcetogaster K. Baer. Two groups, ventral only, of setae per 

 segment. Setae absent from segments 3 to 5. 3rd segment 

 much lengthened. Testes in 5th. Ovaries in 6th. Fresh 

 water. 



0. crystallinus Vejd. Prostomium inconspicuous. (Esophagus 

 nearly as long as pharynx. Transparent. Length 2 to 

 3 mm. 



C. diaphanus (Gruith). Prostomium inconspicuous. (Esophagus 

 short. Transparent. Total segments 14 or 15. Length 10 

 to 15 mm. 



genus Nais Mull., em. Vejd. First dorsal setae on segment 6 : 

 needle-shaped or hooked setae as well as filiform setae in 

 dorsal groups. Testes in 5th. Ovaries in 6th. Fresh water. 



N. heterochceta Benham. Brownish. 2 eyes present : dorsal 

 groups of setae with prong-fork setae. Total segments 31 to 

 41. Length about 6*5 mm. 



N. josince. Vejd. Eeddish. No eyes. Forking of dorsal setae of 

 posterior segments inconspicuous. Length 6 to 8 mm. 

 Scotland ? 



genus Dero Ok. Posterior end of body modified into a respiratory 

 funnel with branchiae. First dorsal setae on 6th segment, 

 rarely on 5th. Testes in 5th. Ovaries in 6th. Fresh water. 



