540 /. PERCY MOORE. 



EXPLANATION OF PLATE XXXIL 



Fig. 32. Surface view of a portion of the circular muscle coat (the longitudi- 

 nal muscle fibres are supposed to have been removed, with the exception of one on 

 each side) of the undivided region of the spermatheca. Haem. X 840. 



Fig. 33. Longitudinal section of the anterior nephridial vesicle. Borax car- 

 mine. X 500. c, the posterior chamber, which would be in communication with 

 the anterior chamber in a section exactly through the median line; m, muscular 

 coat, chiefly of circular fibres. 



Fig. 34. Terminal portion, with external pore, of posterior nephridium; en face 

 and in profile. Free-hand sketch from a living specimen. X about 275. 



Fig. 35. Portion of terminal segment of tubule of the anterior right nephrid- 

 ium, at the point where it passes from the body cavity into the inter-muscular 

 space. Sketch from a living worm. X about 350. The position of the nuclei 

 midway between the lateral caeca of the lumen, the radial striation of a portion of 

 the tubule, the considerable enlargement in size, and the peculiar looping of the 

 lumen are shown. 



Fig. 36. Transverse section across a portion of the anterior loop of the ante- 

 rior left nephridium, showing four tubules and their investment of enlarged peri- 

 toneal cells. The two tubules «, « have a more dense and radially striated pro- 

 toplasm than the other pair, which show a reticulate arrangement. /, a peritoneal 

 corpuscle. Klein, haem. X 500. 



Fig. 37. Oblique section through a single tubule, from the same preparation. 

 X 500. 



Fig. 38. Transverse section of a nephridial nodule from the same preparation. 

 X 500. Showing the intra-cellular plexus, and densely granular protoplasm. The 

 two nuclei are located near the enlarged ends of two simple lumens, where they 

 join the plexus. At these points the protoplasm shows radial markings. 



Fig. 39. Optical section of three nephridial nodules, with the connecting sec- 

 tions of the simple tubule. Drawn with the aid of a camera lucida from a living 

 specimen. The arrangement of the cilia is purely diagrammatic, and a few of the 

 branches of the plexus were added to the camera tracing. The protoplasm and 

 nuclei have, as nearly as could be copied, the appearance shown. X 500. From 

 the anterior right nephridium. t, a short section of one of the loops of a simple 

 tubule. 



Fig. 40. Nephrostome of B. philadelphicus, drawn from a half-grown living 

 specimen under pressure. X 840. m, muscle fibres, to which the nephrostome 

 was attached. 



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