376 MOORE. 



Fig. 12. B. instabilia. A similar section througii part of the somites VII and 

 VIII. The section is somewhat oblique, owing to the natural curvature of the 

 body. X 112. 



VII, minor annulus of somite VII. 



/, lateral flange of somite VIII, made up chiefly of muscle fibres. 



s, longitudinal septum separating a lateral portion of the coelom in which 



the funnel lies; remaining letters as in Fig. ii. 



Fig. 13. B. illuminatus. Part of a transverse section of the 3d somite, 

 showing the position and character of the plexus region of the nephridium. 

 X 112. 



eg, chlorogogue cells. 



ep, epidermis. 



et, sections of efferent tubule. 



tp, first plexus nodule into which the funnel passes. 



Im, longitudinal muscle layer. 



It, long tubule loop. 



/, peritoneal investing cells. 



pn, plexus nodules. 



Fig. 14. B. pulcherrima. Section similar to that represented in Fig. 13. 



X 112. 



t, funnel. 



pn, compacted plexus region. 



Other letters as in Fig. 13. 



Fig. 15. B. philadelphicus. Similar section. X 112. 

 ts, funnel stalk. 



st, short tubule loop. 



Other lettering as in Fig. 13. 



Fig. 16. B. illuminatus. A section through a plexus nodule and accompany- 

 ing tubule. X 500. 



Fig. 17. B. pulcherrima. A section through a portion of the plexus mass. 

 A tubule (i) is shown partly embedded in its substance. X 500. 



Fig. 18. B. illuminatus. A living plexus nodule under slight pressure, show- 

 ing the plexus formed by the lumen. X 500. 



Fig. 19. B. illuminatus. A small portion of the wall of a plexus nodule, 

 showing its vesicular structure ; living and stained with methylene blue. 



