THE NEPHRIDIUM OF LUMBRICUS. 327 



ance of a network ; this is probably the coagulated excretory 

 product. 



The structure of the "bladder/^ or posterior terminal dilated 

 portion, is similar to that of the " body," but the concretions 

 are fewer, and as the external aperture is approached are 

 almost absent ; the walls of this region are, too, provided with 

 muscles. 



The anteriorly directed funnel is very large, and consists of 

 neck and lips. The two lips are dorsally and ventrally 

 situated with regard to one another. The dorsal lip carries a 

 large number of delicate processes, sometimes simple, some- 

 times bifid or multifid, and even arborescent. The ventral 

 lip, on the other hand, is entire ; the slight notches, &c,, in 

 the drawing represent the folds resulting from compression. 



The cells forming the edges of the two lips diflFer ; the dorsal 

 lip is lined by ciliated vesicular cells (fig. 40), similar to the 

 general lining epithelium of the body, but with numerous cilia, 

 and without concretions. 



The cells lining the ventral lip, on the other hand, are 

 short, columnar, pigmented, and ciliated (fig. 39), whilst at the 

 extreme edge the cells become more cubical, large, and are 

 deprived of pigment granules (fig. 38). 



I hope, in the near future, to examine chemically the pro- 

 ducts of excretion in Arenicola and other Polychsetes. 



I have (fig. 36) drawn one of many sections showing ova 

 in the neck of the nephridium ; however, I found none in the 

 body or in the "bladder,^^ and it may possibly be that the 

 funnel merely retains the ova for a period, and does not serve 

 as a genital duct. I think it probable that they really pass 

 to the exterior by the nephridium. 



Cosmovici and Cunningham have given some details of the 

 vessels supplying the nephridium. The nephridial vessel is a 

 branch of the branchial vessel which is given ofi* by the sub- 

 intestinal vessel, much in the same way as in Lumbricus 

 (Cosmovici, loc. cit., figs. 2 — 10). 



The network on the nephridium lies between the excretory 

 epithelium within and the flat ccelomic epithelium outside. 



VOL. XXXII, PART III. — NEW SEK. Y 



