518 F. W. GAMBLE AND J. H. ASHWORTH. 



The anterior portion of the secreting part of the nephri- 

 dium is supplied with blood by a vessel given off from the 

 nephiidial vessel just before entering the nephrostome ; while 

 the posterior portion and the bladder are supplied by the 

 gonidial vessel. The branches of these vessels form a close 

 network upon the nephridiura (figs. 46, 48), which is well 

 developed even in young specimens (Gamble and Ashworth, 

 1898, pi. V, fig. 18). As pointed out by Benham (1891), 

 the network of vessels lies between the secreting epithelium 

 and the coelomic epithelium which covers the nephridium 

 (fig. 49). 



In A. Claparedii there is a tuft of filiform, blmdly-ending 

 vessels given off from the gonidial vessel as it leaves the pos- 

 terior angle of the nephrostome (PI.' 24, fig. 29). These 

 vessels, which are 1 to 2 mm. long, are free at their distal 

 blind ends. They have very thin walls, on some of which 

 small brown cells (probably chlorogogenous) may be seen. 

 A few similar vessels are also given off all along the course 

 of the gonidial vessel, but they are found chiefly in the region 

 of the gonad. A few are also given off the afferent nephridial 

 vessel before it reaches the nephrostome. Similar vessels 

 are also found in A. Grubii in association with the vessels of 

 the body- wall in the region of the nephridia (PI. 26, fig. 64). 

 The blindly-ending vessels given off from the gonidial vessel 

 of A. Claparedii, are probably homologous with the similar 

 vessels which grow out from the gonidial vessel of A. 

 ecaudata, and around which the gonads are developed, 

 thouo-h in the former species these vessels are not associated 

 with the gonad in any way. 



The first three nephridia of A. marina, the first two of 

 A. Claparedii, and the first of A. cristata return blood to 

 the dorsal vessel. The blood from the fourth nephridium of 

 A. marina,^ the third of A. Claparedii, and the second and 



1 Since writing our previous paper (1898) we Lave Found tliatin A. marina 

 the vessel printed in red ou Plate 'i, fig. 5, and lettered N. Eff}, is not, as it 

 appears to be, a blood-vessel with thick walls, but is a solid cord of connective 

 tissue which accompanies the afferent vessel {N. Aff}) of the fourth nephridium 



