SEA-FISHERIES LABORATORY. 315 



so as to show the afferent branch to the nephridium. The 

 afferent vessel of the fourth nephridium is accompanied 

 by a solid cord of connective tissue. x 2. 



Plate IV. 



Fig. 24. Dissection of left side of fifth and part of 

 fourth chaetigerous segments of a Lamiuarian specimen, 

 showing second nephridium with blood-vessels, gonad, the 

 muscles and the ventral nerve cord. Three of the oblique 

 muscles are interrupted to show the nephridium. x 4. 



Fig. 25. Second right nephridium of a young littoral 

 specimen 44 mm. long in dorsal aspect showing especially 

 the capillary network on the funnel and excretory part, 

 the processes on the dorsal lip, the position of the external 

 opening (dotted), and the gonad upon the gonidial vessel. 

 The edge of the ventral lip of the funnel is seen through 

 the dorsal lip. x 65. 



Fig. 26. Fifth rig-Ait nephridium of an adult male 

 in dorsal aspect showing the vesicle distended with sper- 

 matozoa. The funnel of this nephridium was widely open, 

 as is usual at the breeding season. x 4. 



Fig. 27. First left nephridium of a medium-sized 

 worm, in dorsal aspect. This nephridium is much more 

 slender than any of the others. The ventral lip of the 

 funnel is shown (dotted) through the dorsal one. The 

 gonidial vessel bears a number of blindly ending vascular 

 processes which are covered with chlorogogen cells. x 8. 



Fig. 28. The anterior portion of the funnel of the 

 fourth nephridium in ventral aspect. The dorsal lip bears 

 numerous, almost semi-circular, lobed ciliated processes, 

 each of which contains a blind diverticulum of the large 

 blood-vessel which traverses this lip. On both lips there 

 is a network of blood-vessels, but they are shown only on 



