I'ACIFIC COAST OLIGOCir.KTA. 69 



ji. Nephrostomal part. 



Nephrostoine, or funnel. 



Neck of neplirostome, consi.stinj;- of ghindnlar cells. 



Narrow, or nephrostotual duct. 



b. Main glandular part. 



Neck of glandular lobe, connected witli tlie nephrostoraal duct. 



Anterior fold. 



Tlie windings, or tlie coiled [)art of tlie two folds. 



Posterior fold, in wliich the three canals arc of the same size. 



(Spur, with four canals. 



Bridge, with only one canal. 



c. Efferent part. 



Wide terminal-duct or outlet. The latter is frequently furnished with a 



ccelomic bladder. 

 Nephropore. 



When the nephridium is spread out and mounted in glycei-ine it is seen that 

 the canals are of different transparency. Thus the wide canal coming from the bridge, 

 together with its continuation in the spur, is much darker than the two other narrow 

 canals, which are conspicuous through their brilliancy. These two white canals meet 

 in the very apex of the spur, while the two darker canals meet a little further in. 

 The greater obscurity of the wider canal is partly due to ciliation. 



The nephrostome of Pluinicodrilus taste is furnished with a large neck, almost 

 as large as the rosette, containing several very hirge cells with conspicuous nuclei. 

 The nephrostome is about as long as the narrow tube. 



In size the nephrostome ranges with the very largest, it being conspicuous 

 and readily dissected. 



The marginal cells vary in number between eight and fourteen. There is a 

 larger central nucleus as usual. The glandular neck of the nephrostome contains 

 two of these nuclei much larger than any of those found in the rosette, though it also 

 contains several smaller ones. When the body of the annelid is laid open and viewed 

 from above, the nephrostomes are seen to lie on their side as in fig. 9, the side of 

 the thick rim of the rosette being uppermost. In order to see the rosette flattened 

 out it is necessary to dissect out the nephrostome, which operation in this species is 

 not particularly difhcult, as the muscular tissues easily separate. 



The peritoneal covering of the posterioi' nephridia separates itself in two dis- 

 tinct masses, one dorsal and one ventral, the latter being somewhat the smallest. At 

 the point where they join the peritoneal covering has narrowed down to a narrow 

 band connecting the two main parts. 



The upper peritoneal mass does not surround or contain any of the canals or 

 ducts, but a])pears to be merely an api)endage, a gland, as it were, engrafted on the 

 lower part. The canals and tubes are entirely confined to this part, as is also the case 

 in the nephridia of Ocuerodrilus and Kerria. 



