THE NEPHRIDIA OF THE POLYCH^TA. 715 



kidneys and as genital ducts^ obviously formed by the 

 grafting of a large funnel on to the inner extremity 

 of an originally complete nephridium. 



FuRTHEE Observations on the NEPHXHYiDJi;. 



On examining some sections cut through aNephthysceeca, 

 Fabr., which had previously been injected with some Indian 

 ink, I found that the amoebocytes of the ccelomic fluid, 

 charged with insoluble black particles, were accumulated at 

 the base of each genital funnel (ciliated organ), and were for 

 the most part enclosed in a sac formed by a double layer of 

 flat ccelomic epithelium (fig. 33). Into this sac enters the 

 ciliated organ, forming its posterior lining. The internal 

 end of the nephridium with its solenocytes lies quite near, 

 and rather above it; the nephridial canal passes just behind. 

 The sac is, no doubt, homologous with the " nephridial 

 sac ^' of the Glyceridse (12, p. 446), but it is a much less 

 differentiated organ, being merely a sort of pocket in which 

 the loose cells are accumulated by the action of the cilia of 

 the genital funnel, which thus brings together waste products 

 within easy reach of the nephridium.^ 



Polygordiidee. 



Adult specimens of Polygordius neapolitanus and P. 

 appendiculatus were studied at Naples and here in Oxford. 

 The only living larvEe I have been able to examine were 

 obtained by me at Trincomalee last summer, and belong to an 

 unknown species. 



' Since these observations were made, Mr. Stewart has published a paper 

 on the nephridium of Nephthys cseca (24), in which he describes the 

 accumulation of loaded phagocytes at the base of the genital fuunel. He 

 does not, however, appear to have seen the sac, which was, perhaps, not 

 present in his specimen ; and he believes the phagocytes to pass into the 

 lumen of the nephridial canal. 



In this paper Mr. Stewart corrects the representation I gave of the vascular 

 supply of the nephridium in a diagram (11, fig. 8). The blood-vessel marked 

 d. I. V. should come off further from the nephridium, and the blood-vessel 

 marked v. I. v. nearer the ciliated organ — as shown in my figure 7 (11). 



