350 MOORE. [Vol. XIII. 



The first (Fig. i, ef^, et~) is very conspicuous in extracted 

 living nephridia of B. illuminatus, in which it can easily be 

 traced from the inner limb of the short tubule, passing first to 

 the parietal side of the first two or three plexus nodules, then 

 appearing on the intestinal side of the main plexus lobe, along 

 which it passes in a groove as before described, pursuing a 

 slightly sinuous course to the point of attachment of the funnel, 

 where it leaves the plexus region and passes into the free 

 coelomic section. This latter in B. illuminatus forms two folds, 

 which closely embrace the funnel stalk (Figs, i, 6), and in B. 

 instabilia (Fig. 9) a more complex coil, from which only the end 

 of the funnel projects. These folds are firmly bound together 

 and to the funnel by their investments, so that they cannot be 

 disengaged without injury. There is, however, no actual fusion 

 of the walls. In B. illuminatus the tubule is sometimes thick- 

 ened in this region, and cross sections present the appearance 

 shown in Plate XXII (Fig. 23, et^). The remainder of the 

 coelomic tubule is a free loop which bellies ventralwards and 

 reaches to the body-wall of the third somite (in the case of the 

 anterior nephridium first penetrating the septum), where a slit- 

 like opening between two of the longitudinal muscle fibres 

 permits it to enter the intermuscular space. It is interesting 

 to note that in B. illuminatus the tubule enters the body-wall 

 at the level of the ventral opening of the lateral glands, and 

 imm_ediately anterior to those of the third somite. As the 

 nephridio-pores of the Enchytraeidae, etc., always open just 

 anterior to the ventral setae bundles, and are always reached 

 by a 'duct which passes directly through the body-walls, this 

 fact is further evidence that the lateral glands are homologous 

 to the setigerous glands of the Enchytraeidae. Hubrecht (23) 

 has shown the interesting condition in Lumbricus and Allollo- 

 bophora, that while the nephridio-pores lie at any one of three 

 levels, the efferent nephridial ducts all enter the body-wall at 

 the same level, which is the lowermost of the three, and undoubt- 

 edly the original one, and pass thence to the upper two levels 

 between the muscular layers of the body, just as they do in the 

 case of the anterior nephridia of the Discodrilidae. The pos- 

 terior nephridia, however, retain the primitive opening at the 



