THE STRUCTURE AND AFFINITIES OF SACCOCIRRUS. 419 



The nephridium in the female is a slender tube running 

 in the angle between the oblique muscles and the body-wall, 

 to open forwards into the coelom through a septum (figs. 3 

 and 22). In the genital segments (intestinal region), when 

 it reaches a point nearlj^ opposite the sperraathecal pore, the 

 nephridium turns sharply downwards, passing between the 

 epidermis and the longitudinal muscles, until it touches the 

 spermathecal duct, into the very base of Avhich it opens (figs. 

 3, 6, 21, and 14). This downward limb of the nephridium 

 becomes very narrow, having a much diminished lumen 

 towards the minute opening. The wall of the nephridium is 

 formed of granular, much vacuolated protoplasm ; a few cilia 

 are seen in the lumen (fig, 3). There is no projecting lip 

 to the funnel, which merges rapidly into the epithelium 

 covering the septum (in my specimens, which were not quite 

 mature). Round the opening are long cilia passing down 

 into the lumen of the canal (fig. 3). 



In the male the cavity of the penis is lined with granular 

 cells, and its wall is strengthened by a number of delicate 

 refringent cuticular rods pointed at both ends (figs. 8 and 9). 

 The sperm-sac and nephridium do not form one continuous 

 duct, as described by Marion and Bobretzky. Coming off 

 from the penis is a ciliated duct, which soon widens out into 

 a pear-shaped sac lying, unlike the spermatheca, entirely in 

 the lateral chamber of the ccelom (figs. 9, 10, 11, and 14). 

 This sperm-sac contains ripe spermatozoa, and ends blindly 

 at its swollen extremity. In the genital segments the 

 nephridia, quite similar organs to those of the female in 

 their general structure, open into the duct of the sperm-sac 

 near its entrance into the penis. The funnel in these seg- 

 ments is much enlarged, richly ciliated, and spreads for a 

 considerable distance over the anterior face of the septum 

 (figs. 9, 12, and 14). 



Small-funnelled nephridia are found in both sexes in the 

 segments of the oesophageal region, beginning after the first 

 bundle of chaetoe (fig. 15). But whereas in the male they 

 open dorsally, at the level of the penis in the more posterior 



