i9 I 7-] Fauna of the Chilka Lake : Oligochaeta. 487 



The dorsal vessel is ventro-laterally or laterally situated , on the left side of the 

 alimentary tube, throughout the greater part of the body; it appears in a mount of 

 the whole animal as a series of loops, the bend of each loop being at about the level 

 of the lateral line of the body and the rest of the vessel below this level ; it becomes 

 altogether lateral in position about segment vii, and is only really dorsal at the an- 

 terior end of the body. Supra- and subintestinal vessels are absent. The parietal 

 plexus is situated amongst the muscular fibres of the body- wall, well beneath the 

 peritoneal layer. The valves in the larger vessels have been described in related spe- 

 cies by previous authors (Goodrich, 4; Nomura, 7). 



The Enchytraeid character of the nephridia in this genus is well known. The 

 remarkable length of the upper lip of the funnel is not to be made out in preserved 

 material. 



The anterior lobes of the cerebral ganglion project forwards for some distance, — 

 about 30 /s — in front of the main mass; there are practically no posterior projections. 



The testes are situated in segment x, along with the cup-shaped funnels and a 

 quantity of sperm-morulae. The vas deferens is at first, immediately behind the 

 septum, 25^ in diameter, and without any covering of high peritoneal cells ; but this 

 uncovered portion is of very small extent, — scarcely even as long as the width of the 

 tube. 



The second portion of the duct, or the part which is covered with elongated 

 peritoneal cells, passes backwards for some distance ventrally in the segment, and 

 then rises towards the dorsal body- wall. The investment of high cells ceases just 

 before the tube reaches the highest point of its course. In this part of its extent the 

 canal with its investment has a diameter of 90 to 120^ by 50/x ; the central tube is 

 about 35/u thick, the peritoneal covering accounting for the remainder. The cells 

 composing the wall of the tube are columnar, about twice as high as broad, and fur- 

 nished with long cilia ; the peritoneal cells are apparently only one layer thick, and 

 very much elongated i — sometimes as much as 40^ in length ; where they appear to be 

 more than one layer thick the section is probably oblique ; their cytoplasm stains 

 darkly and equably, and the nucleus is at about half the height of the cell. 



The third portion of its course, which is free from the tall peritoneal investment, 

 comprises the summit of the curve and the downward course of the canal until it 

 joins the atrial chamber. Its total length is about ioo/*, and its diameter at first 35 

 to 40ju, but it becomes narrower before joining the atrial chamber, measuring at its 

 end 23 ix ; from the bend downwards it is heavily ciliated. 



The atrial chamber is of an elongated pear- shape, the narrower end below ; the 

 lower ends of both converge to unite in the middle line, and forming there a narrow 

 tube, discharge, as described by Moore, on the summit of a low papilla on the roof 

 of the spermiducal chamber; the union of the atrial chambers takes place below the 

 ventral nerve cord and ventral vessel. Each atrial chamber is 145^ long and yo/x in 

 diameter at its thickest part; its upper end is at about half the height of the segment; 

 it is lined by a very high non-ciliated columnar epithelial layer, so that the clear lu- 

 men in the middle is not more than about 20/x across. There are well-marked circu- 



