32 



E. NOMUltA : 



1 - 



d.v 



cell runs out a fine excretory duct, which passes between the cells 

 of the inner epithelium and opens into the atrial lumen. No distinct 

 peritoneal layer can be observed in the atrial wall, but it is 

 represented by some diffusely scattered cells of the prostate glands. 



At the dorso -posterior end of the atrium in segment XI com- 

 mences the atrial duct portion, which thence extends dorso-ventrally 

 towards the body wall behind the dorsal seta-bundle. Then it 

 descends and undergoing a few windings opens into the dorsal 

 portion of the lateral horn of the spermiducal chamber. Some 

 muscle fibres arising from the 

 musculature of the body wall art' 

 attached to the summit of the 

 duct portion and hold the whole 

 male duct in its position in the 

 cœlom. The structure of the atrial 

 duct portion is the same as that 

 of the vas deferens. 



The spermiducal chamber is a 

 large organ in the ventral median 

 plane of segment XI (figs. 25, 

 26, 27). We may distinguish 

 four parts of the organ : viz. a 

 transversal bridge, two lateral 

 horns and a median chamber. 

 The transversal bridge lies trans- 



tb n.c nip 

 Fig. 27. 



Schematised cross section of segment XI, 

 to show the posterior part of the male duct 

 as seen from the anterior side. xlOO. An- 

 terior portion of the duct iî omitted, ps — 

 posterior sperm-sac, d.v — dorsal vessel, mf — 

 muscle fibres, d.p — atrial duct jjortion, dh — 

 dorsal portion of the lateral horn, ph — posterior 

 portion of same, i.n — intestinal vascular net- 

 work, tb — transversal bridge, n.c — ventral 

 nerve cord, v v— ventral vessel, mp — male 

 pore. 



versely across the body axis 

 and lies at the distance of about two-thirds of the segment from 

 the anterior septum. It is almost circular in cross section, which 

 is about twice as large as that of the vas deferens. "When the 

 worm is young or protandrously matured it makes a shallow 

 obtuse angle at its middle, but as the ova ripen the angle 



