THE DISCODRILID NEPHRIDIUM. T^jg 



EXPLANATION OF PLATE XXIIL 



Fig. 40. B. instabilia. Transverse section of one of the anterior nephridial 

 vesicles. X 500. 



Fig. 41. B. illuminatus. Semidiagrammatic figure to show the relation of a 

 post-genital nephridio-pore to the lateral gland. Reconstructed from two vertical 

 sections. 



np, nephridio-pore. 



g, opening of lateral gland. 



Fig. 42. B. illuminatus. Profile {a) and face (b) views of the vesicles of a 

 posterior nephridium, living. A cluster of excreted granules is shown at g. X 

 about 275. Taken from Journal of Morphology, vol. x, no. 2. 



Fig. 43. B. philadelphicus. Dorsal view of the anterior unpaired vesicle in 

 situ, showing a portion of the efferent duct of one side. X 500. 



ec, pore by which the lumen of the efferent duct communicates with the cav- 



ity of the vesicle. 

 en, nucleus of efferent duct. 



ed, diverticula of lumen of duct. 

 g, gland cells. 



vl, cavity of vesicle. 



«/, nephridio-pore. 



Fig. 44. B. philadelphicus. A vertical section through the vesicle in a trans- 

 verse plane of the body, shovring the relation of the vesicle to the intermuscular 

 space and the efferent ducts of the two nephridia. X 500. 



c, cuticle. 



cm, circular muscle fibre. 



ct, connective tissue, nuclei, and sheath. 



ep, epidermis. 



et, efferent tubules meeting the vesicle at ec. 



g, glandular cells. 



Ime, external longitudinal muscle fibres. 



Imi, internal " " " 



m, isolated muscle fibres related to ducts. 



np, nephridio-pore. 



/, parietal peritoneum. 



ve, epithelial lining of vesicle. 



vm, muscular sheath of vesicle. 



Fig. 45. The same. A transverse section (in a horizontal plane of the body). 

 X 500. 



eg, portion of a skin gland. 



Other lettering as in Fig. 44. 



Fig. 46. The same in vertical longitudinal section of the body. X 500. 

 Lettering as in Fig. 44. 



Figs. 47, 48, 49. B. illuminatus. Outlines of the living vesicle from the side 

 and from above. 48 in diastole, 49 outline in systole. X 500. 



