NEPHRIDIA OF CERTAIN EARTHWORMS. 411 



Fig. 11. Section through a portion of nephridial tube, highly magnified. 

 bl. Blood-vessel, n. Marks the boundary between the region of the 

 nephridium with an intracellular duct and that with an intercellular 

 duct. 



PLATE XXXI. 

 Figs. 12 — 14. — Perichaeta aspergillum. 



Fig. 12. Diagram of the relations of the nephridiopores (o) to the setae 



(s), as seen on a superficial view. 

 Fig. 13. Diagram of the nephridial network in several segments, o. Ne- 

 phridiopores. p. Nephridial network, s. Intersegmental septa. 

 Fig. 14. Diagram to illustrate the disposition of the nephridia in a single 

 segment as seen in transverse sections, s. Setae, o. Nephridiopores. 

 Fig. 15. -Acanthodrilus multiporus. — A diagram corresponding to 

 the last. s. Setae, n. Nephridiopores. 



