139 



terior end of the diverticles there is a large valve opening into the 

 sacculated intestine." 



It does not appear from any information which can be gleaned 

 from the literature on this subject that the structure of the intestinal 

 diverticula in //. iirbancnsis is like that of any other species. 



Dorsal Vessel. — The dorsal blood-vessel arises from the perivis- 

 ceral blood sinus in IX. At its origin, and extending somewhat into 

 VIII, is a very large heart-like expansion which in the specimen stud- 

 ied is filled with some substance — probably the remains of the blood. 

 In the posterior part of VIII this swelling decreases rapidly and the 

 dorsal vessel proper appears, lying near the mid-dorsal line of the ali- 

 mentary canal. Immediately anterior to the third pair of septal glands 

 there is another, but less prominent, expansion of the vessel. This also 

 soon becomes reduced to the usual diameter. The greater part of the 

 external surface of the vessel is covered by chloragog cells. The 

 marked change in the diameter of the vessel in VIII is accompanied 

 by marked changes in the walls of the vessel. In the anterior part 

 of VIII the vessel is thick-walled, its external surface is covered with 

 chloragog cells, its inner surface has a number of cells projecting 

 radially into the lumen, and it is of the usual diameter. Near the 

 middle of VIII there is a sudden change in which the diameter in- 

 creases greatly, the wall decreases in thickness to a mere membrane, 

 the chloragog cells are lost, and the only cells which can be identified 

 in connection with the walls are the few cells which lie flattened against 

 or are contained within the extremely thin wall. 



Nephridia. — The anteseptal part is small, the postseptal part is 

 large, broad, and somewhat pointed at the posterior extremity. The 

 efferent duct arises from the postseptal part, near the septum, and 

 usually is about as long as the former. The internal lumen is tortuous 

 throughout its entire length. The right nephridium on XIII/XIV is 

 missing. This is probably due to the fact that that side of the body 

 is filled with developing egg-masses, this producing a crowded condi- 

 tion which has brought about the elimination of the nephridium. 



Spcniiidiical Funnel. — The spermiducal funnel lies in the ventral 

 part of XI with its base in close proximity to XI/XII. It lies close 

 to the body wall and parallel to the long axis of the body. It is about 

 two and a third times longer than the diameter, the length being 0.192 

 mm., and the diameter 0.085 "''"''• The sperm duct is long, much con- 

 torted, and confined to XII. 



Penial Bulb. — This organ (PI. XII, Fig. 58) is of the lumbricillid 

 type of structure. It lies in the usual position in the ventral part of 

 XII, on a deep invagination of the body wall. It is large in compari- 



