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MANUAL OF ELEMENTARY ZOOLOGY 



nephrostome consists of a large crescentic central cell with 

 a rim of marginal cells around it arranged so as to surround 

 a crescentic, funnel-shaped opening, turned to one side. 

 The funnel is ciliated, and from it there leads backwards 

 a narrow ciliated tube. This passes through the septum 

 to the main part of the nephridium, which lies behind the 



deb. 



p.e 

 B 



Fig. 141. — The nephrostome or funnel of a nephridium of the earth- 

 worm. A, in surface view, highly magnified ; B, in longitudinal 

 section, diagrammatic. 



cen.c, Central cell ; deb., ddbris of coelomic corpuscles and excretory granules being 

 swept into the funnel; ?».£., marginal cells; />.*., peritoneal epithelium; />.£., 

 vesicular connective tissue cells; jr., point at which the marginal cells join the 

 lining of the tube, which turns over round the opening. 



septum, in the ccelom of the next segment, opening to the 

 exterior by the nephridiopore in that segment. The narrow 

 part of the tube is long and winding and loses its cilia in 

 places. It is followed by a wider, short, brown region, 

 ciliated throughout, this by a still wider tube which is not 

 ciliated, and finally a short, very wide, muscular tube leads 

 to the nephridiopore. The whole tube, except the muscular 

 region, is formed of hollow cells shaped like drain pipes 



