CHAETOPODA 



141 



of the ventral middle line (Fig. 90). The testes are similarly 

 built up from peritoneal cells, situated on both sides of the 

 oblique septa, in the segments which succeed the seventh. 



Fig. 89, — Polygordms ni 



A. The living animal, x about 5. 



B. Anterior end of the worm seen from the 



right side, more highly magnified. 



1. Prostomium. 



2. Peristomium. 



3. Tentacle. 



4. Setae on tentacle. 



5. Ciliated pit. 



C. Ventral view of the same. Numbers 



as in B. 



6. Mouth. 



(After Fraipont.) 



D. Portion of body, showing 



1. Segments separated by grooves. 



2. Grooves. 



E. Ventral view of posterior end, show- 



ing the last three segments. 



1. Segment. 



2. Groove. 



3. Anal segment. 



4. Anus. 



5. Ring of papillae. 



Histriodrilus, which lives parasitically upon lobsters' eggs, 

 is somewhat more highly organised than Protodrilus. The 

 body is differentiated into regions, the nervous system has 



