THE NEPHEIDIUM OF LUMBRICdS. 295 



loops, will be readily seen by a glance at fig. 2, which will 

 convey more information than any verbal description. I will, 

 therefore, pass on to the histology of the various parts. 



I will premise that, with the exception of the funnel itself, 

 or rather a part of the funnel, together with probably the mus- 

 cular duct, the canal of the nephridium is "intra-cellular," 

 i. e. the nephridium consists of a large number of perforated 

 or "drain-pipe" cells, placed end to end (see PI. XXIV, figs. 

 30, 31, 32). The size of the cell and the relative proportion 

 occupied by the lumen constitute the main morphological 

 differences observable in the various regions ; but the character 

 of the protoplasm is of very great physiological importance, 

 although we do not fully know the exact function of each 

 region. 



2. The Structure of the Various Regions. 



I. The Prseseptal Portion. — The nephrostome or funnel 

 is carried at the end of the short portion of the " narrow tube '' 

 which passes through the anterior septum bounding a given 

 somite. The character of this portion of the tube will be 

 described below. This prseseptal portion of the tube is sur- 

 rounded by a mass of vesicular cells, the outlines of which are 

 readily seen in the living condition, and frequently in stained 

 preparations. These cells resemble those coating the post- 

 septal portion, and appear to be similar to those described and 

 figured by Kukenthal round the vessels and uephridia of 

 Tubifex (24), and not improbably they have the same 

 meaning. The superficial cells are usually flattened, and 

 form a ccelomic epithelium continuous with that covering the 

 septum. 



The funnel (PI. XXIII, figs. 4—7, and 32) has recently 

 been figured by Goehlich (20) in some detail, but he has alto- 

 gether misunderstood the appearance represented. As is well 

 known, the funnel consists of a number of very long, narrow, 

 somewhat wedge-shaped cells — which I shall call "marginal 

 cells" — arranged around a central point. The nucleus in 

 each is placed near the outer end of the cell, which is rounded 



VOIi. XXXII, PAKT III. — NEW SEE. U 



