166 



the ental surface, and form a layer of which the continuity is broken 

 only by the apical parts of the chylus cells. No interstitial cells are 

 present. 



Nephridia. — The nephridia appear first on VI/VII. The ante- 

 septal part (PL XI, Figs. 44, 45) is well developed, ovate, and pro- 

 vided with a distinct ciliated nephrostome. The postseptal part is 

 longer and slightly larger than the anteseptal part. There appear 

 to be two divisions in the former ; an anterior smaller one and a pos- 

 terior larger one. The smaller region is a kind of neck by which the 

 posterior large one is joined to the anteseptal part. The origin of the 

 efferent duct presents an interesting feature. It becomes distinct from 

 the ventral surface of the postseptal part at about the middle of its 

 length. A critical examination of the nephridia in the various parts 

 of the body and in the various specimens reveals two rather distinct 

 features which seem to throw light upon the true origin of the duct. 

 A number of nephridia were studied in which it was evident that the 

 posterior end of the nephridium was reflected ventrad upon itself 

 (PI. XI, Fig. 44) for some distance and then diverged as the duct 

 proper, thus pointing to the fact that the duct really arises from the 

 posterior end of the postseptal part. It should be noted that this 

 reflected portion meets and attaches itself to the ventral side of the 

 nephridium proper, the line of union appearing in sections only as 

 a single line of fusion. Quite a number of nephridia were found (PL 

 XI, Fig. 45) in which the above-described condition of the caudal 

 end of the postseptal part was not shown, the duct arising from the 

 ventral surface of the postseptal part about midway of its length. 

 This variation may be interpreted by regarding the first condition as 

 the transitional stage and the second one as the resulting one. An- 

 other interesting observation is connected with the efferent duct, a 

 small but distinct reservoir being present at its ectal extremity. Just 

 before the lumen of the duct reaches the exterior it expands into a 

 more or less flask-shaped resen'oir which in turn opens to the ex- 

 terior through a small pore. The lumen of the nephridium is much 

 longer and more contorted in the postseptal than in the anteseptal 

 part. 



Spermidncal Funnel. — The spermiducal funnel (PL XI, Fig. 49) 

 is cylindrical, usually slightly bent, and approximately twice as long 

 as the greatest diameter. There is a distinct collar set off from the 

 body of the funnel by a constriction. This collar is not reflected, but is 

 funnel-shaped. 



Penial Bidb.—The penial bulb (PL XII, Fig. 51) is of the lum- 

 bricillid type. It is rather simple in its structure and moderate in 



