294 W. BLAXLAND BENHAM. 



Contents of Paper. 



1. Nomenclature of the parts of the nephridiuna, and the course of the 



various regions. 



2. Histology of the various regions, and suggestions as to their function. 



3. Comparison with the nephridium in other genera. 



4. The nephrostome of Perichseta malamauiensis, n. sp., and other 



genera. 



5. Circulation in the nephridium. 



6. The nephridium of Arenicola. 



1. Nomenclature of the Parts and Course of the 

 Various Regions. 



The long winding tube which constitutes the excretory 

 organ of Lumbricus is for the most part embedded in a 

 coating of vesicular cells, which are in their turn surrounded 

 by the pavement-cells of the coelomic epithelium. The tube 

 is, in its adult condition, as in its development, divisible into 

 two portions: (I) a prseseptal portion, consisting of the in- 

 ternal funnel or nephrostome and a short ciliated tube; and 

 (II) a much more extensive post-septal portion. The latter is 

 readily distinguishable into four regions : (1) the very long 

 but narrow tube in continuity with the prseseptal tube; (2) 

 the short brownish ciliated middle tube; (3) the wide large 

 tube; and (4) the muscular tube or duct, which opens to 

 the exterior. The first three of these tubes (1, 3, 3) are twined 

 about in rather a complicated but quite constant manner, and 

 are bound together by the coat of vesicular cells in such a way 

 as to form two great " loops," visible fairly distinctly with the 

 naked eye when an opened worm is covered by spirit. Another 

 "loop" is formed by the muscular duct (4). This last I will 

 call the " first loop " (e, figs. 1, 2, 3) ; the " second loop " 

 (f) contains the greater part of the narrow tube (1), and of 

 the large tube (3) ; finally, the "third loop" (g) consists of a 

 part of the narrow tube, a part of the large tube, and the 

 whole of the middle tube (2). 



The course taken by these various regions, from the funnel 

 to the external aperture, and the relations of the tubes to the 



