PHYLUM NEMATHELMINTHES 



<53 



and giving off six nerves forwards and six backwards (Fig. 

 83). Of the latter, two are 

 of a considerable size and 

 run in the dorsal and ven- 

 tral lines respectively {din, 

 vlri) . 



The reproductive organs 

 are formed on a peculiar 

 and very characteristic pat- 

 tern. The testis (Fig. 84, 

 is) is a long coiled thread, 

 occupying a considerable 

 portion of the body-cavity. 

 At its posterior end it is 

 continuous with the vas 

 deferens. The vas deferens, 

 in its turn, becomes con- 

 tinuous with a wide canal, 

 the vesicula seminalis (vs. 

 sent), which opens by a 

 short, narrow, muscular 

 tube, the ductus cjaculato- 

 rins, into the rectum. Be- 

 hind the rectum, and open- 

 ing into its dorsal wall, are 

 paired muscular sacs (s) 

 containing the penial seta 

 (p. ns) already noticed. 

 The anterior end of the 

 testis consists of a solid 

 mass of sexual cells ; pass- 

 ing backwards there is 

 found a cord or rachis occupying the axis of the tube and 



