SEA-FISHERIES LABORATORY. 249 



the first nephridium, and after traversing the neplirostome 

 and the excretory part of the organ ramifies finally on 

 the body wall near the nephridial longitudinal vessel, or 

 opens into the latter. The funnel of the first nephridium 

 is also connected with the ventral vessel. Similar 

 branches of the dorsal vessel pass to the second and third 

 nephridia, and have a course corresponding to that con- 

 nected with the first nephridium. A branch of the 

 ventral vessel enters the funnel of each of these two 

 nephridia a little in front of the middle of its length. 

 Just behind the heart the ventral vessel gives off a branch 

 which forks near the fourth neplirostome, one part passing 

 to the dorsal longitudinal vessel, and the other taking 

 the usual course through the funnel and the excretory 

 part of the organ to the nephridial longitudinal vessel. 

 Similar branches of the ventral vessel are given off to the 

 fifth and sixth nephridia, but these send afferent branchial 

 vessels to the first and second gills before entering the 

 nephridia. Their course in the nephridia is as described 

 for the corresponding vessel in the fourth nephridium. 



Connected with all the nephridia there is also a small 

 branch from the dorsal longitudinal vessel, which enters 

 the anterior part of the excretory portion of the organ and 

 ramifies there. This vessel is apparently sometimes 

 missing from one or more of the nephridia. 



The vessel which enters the funnel of the nephridium 

 gives off a branch to the ventral lip, but the main trunk 

 traverses the dorsal lip close to its edge, sending a blind 

 vessel into each of its ciliated processes. Numerous 

 branches are given off from the main vessel in both the 

 dorsal and ventral lips, forming a close network ; some of 

 the vessels on the nepkrostonie have blind dilated termina- 

 tions (fig. 28). After traversing the dorsal lip of the 

 nepkrostonie, the large vessel leaves it at its posterior 



