BY SARAH O. BHENNAN. 695 



outgrowths of the posterior septum of segment ix., the posterior 

 (p.s.s.) are outgrowths of the anterior septum of segment xii. They 

 are comparatively large, smooth, white bodies, which are prolonged 

 into finger-shaped processes, terminating in whip-like extremities. 

 The cavity of each is divided up into a series of inter-communi- 

 cating compartments in which developing sperms also occur. The 

 full}' developed sperms, with an average length of -07 mm., become 

 attached in bundles by their heads to the ciliated epithelium of 

 the rosettes. In the immature sjDecimen the sperm reservoirs 

 have already attained the adult condition, while the seminal 

 vesicles are represented by small digitiform outgrowths of the 

 septa. 



(d) Spermiducal (Prostate) glands. — These are, as Fletcher 

 describes, a pair of large flattened bilobed masses situated in 

 segment xviii., and confined to that segment (fig. 1, sp.y.). The 

 lobes are invested by peritoneum and are richly supplied with 

 blood vessels. They present the usual structure, i.e., the finer 

 ductules into which open the large glandular cells unite to form 

 larger ducts, and these eventually unite to form a single main 

 duct. This latter, directly after its foi'mation, penetrates the 

 body wall and opens to the exterior on a prominent papilla on the 

 ventral surface of segment xviii. All the ducts are lined by a low 

 columnar epithelium. There do not appear to be any specialised 

 genital or penial seta? in the neighbourhood of the spermiducal 

 apertures. The base of the anterior lobe of each gland is 

 traversed by the vas deferens, which, as alread}' mentioned, opens 

 into the main duct just after its formation. 



In the before-mentioned immature specimen the prostate is 

 represented by the common diict, from which sprout out a small 

 number of slightly-branched blindly-ending tubes lined by 

 columnar epithelium. There is as yet no ti^ace of the proper 

 prostatic cells. 



Clitellum. — The clitellum extends from segment xiii. or xiv. 

 to xviii. Histologically it presents no features of special 

 interest. 



