No. 3-] THE DISCODRILID NEPHRIDIUM. 333 



seen that the inner lobe, with its two loops reaching to the 

 septum ^"/viii corresponds to the long lobe of four tubules, 

 while the outer corresponds to the smaller lobe of three tubules 

 doubled on itself. The two are then bent around the granular 

 mass and more compacted. The pairing of the tubules is also 

 less distinct, as they often separate and pursue more or less 

 independent and often highly irregular courses. 



European authors have described the tubules as ciliated 

 throughout, even the efferent duct being so described by 

 Lemoine and figured by Dorner.^ Such is not the case, how- 

 ever, in American species, in which the efferent duct, that por- 

 tion of it at least which lies in the body-walls, is entirely 

 without cilia. The same is true for the greater part of the 

 short tubule loop, while in the longer loop the cilia are arranged 

 at regular intervals in widely separated groups. The bewilder- 

 ing activity of the ciliary action in all parts of the organ as it 

 lies folded within the body might well lead one, on superficial 

 examination, to suppose that the ciliation was general; and 

 doubtless it will be found that B. parasita does not differ from 

 the American species, which approach the usual oligochaetous 

 plan in the scattered arrangement of the ciliated tracts. 



2. Analysis of a Nephridiiun of Bdellodrihis illitviinattcs . 



The foregoing, in addition to describing the general arrange- 

 ment of the nephridia in American forms, contains practically 

 a summary of the morphological facts furnished by former 

 writers. Before describing in detail the minuter structure of 

 the nephridium, it will be well to proceed to its analysis, select- 

 ing as a type a species in which this is easily accomplished, and 

 then to consider each region in turn. 



Referring to the figure of Bdellodrilus illuminatus (PI. XX, 

 Fig. i), and to the simplified diagram (Fig. 2), and beginning 

 at the inner end (that most remote from the external pore), we 

 find the ciliated funnel (/) containing the nephrostome (im), and 

 passing into a narrow tubular neck (ts), which is connected 

 with the yellow granular mass, not highly opaque in this species. 



1 Voinov (1. c.) has corrected these statements, finding in B. parasita a distribu- 

 tion of the cilia similar to that here described. 



