334 MOORE. [Vol. XIII. 



This mass is seen in B. illuminatus to be in reality a complexly 

 folded and beaded section of the tubule {rnp, ap') composed of 

 swollen and highly granular nodules {pn) alternating with short 

 narrow sections {ct). As the lumen breaks up within each of 

 the nodules into canalar plexuses, we may designate this the 

 plexus region, in which we distinguish a main plexus lobe {mp, 

 mp") and an accessory plexus lobe (ap, ap'), the latter of which 

 is connected with the system of spreading tubules which con- 

 stitute the most noteworthy part of the organ. The tubule 

 arising from the external end of the plexus is the outermost of 

 a group of three {si, si) which is closely associated with the 

 accessory plexus lobe, and which will be denoted the small 

 tubule lobe. Leaving this and passing directly away from the 

 plexus region, the first tubule reaches to the farthest point to 

 which the nephridium extends, then turning on itself forms a 

 recurrent canal which returns to the starting-point, becoming 

 there the middle tubule of the small lobe; but bending once 

 more as the innermost tubule of this lobe, it retraces the course 

 nearly to the farthest point reached, and then returns as a second 

 recurrent tubule to the plexus region, but not this time into 

 the smaller tubule lobe. Thus is constituted the large tubule 

 lobe (//, //), composed of four tubules arranged in two loops 

 which communicate at their proximal ends by means of a short 

 connecting tubule {cct). Of the two loops the second one is 

 the shorter {st, si), and may be said to constitute an axis, about 

 which the other is arranged and beyond which it extends. The 

 latter is therefore much the longer loop (li, It). 



From the proximal end of the recurrent limb of the shorter 

 loop the tubule {eU, cf^) proceeds along the axis of the main 

 plexus lobe to the point of attachment of the funnel stalk, 

 where it connects with the coelomic portion of the efferent 

 duct {ef^, eti), here thrown into a loop which embraces the 

 neck of the funnel. Passing from this point to the body-wall, 

 it perforates the longitudinal muscular layer, and proceeds 

 dorsalwards in the intermuscular space to the common vesicle 

 by which it opens with its fellow to the exterior {etz). 



We have now traced the nephridium through all its parts, and 

 have found that it is throughout a continuous tubule, in which 



