ON THE NEPHRIDIA OP THE POLYCH^TA. 451 



carmine or Indian ink. In such worms the nephridial sacs are 

 found to be crammed with cells loaded with particles of these 

 substances. I have noticed that many of the loaded amoeboid 

 cells make their way into the csecum. 



There can be no doubt, then, that solid waste matters are 

 accumulated in the nephridial sac. We may now ask what 

 becomes of them when they have reached this cul-de-sac. 



In connection with this question I may now describe 

 another peculiar variety of cell which occurs in the nephridial 

 sac and its csecum. These cells are large, and generally^of an 

 irregularly oval flattened shape ; they are distinguished by the 

 possession of an immense number of minute colourless 

 granules, giving the whole cell a characteristic greyish appear- 

 ance (fig. 23). They are seen in numbers creeping over the 

 inner surface of the nephridial sac (figs. 3, 18, and 19, gr. c), 

 and also in the secondary chambers of the sac and csecum. In 

 the latter position, indeed, they are always found, sometimes 

 being flattened against the walls, and at other times piled up 

 in rows (figs. 19 and 20, (jr. c). The nucleus of these finely 

 granular cells is often of very remarkable appearance, being 

 most irregular in form, like a hollow sphere, or very frequently 

 bent round so as to form a horse-shoe shape (figs. 18 and 20). 



Appearances have led me to believe that these cells originate 

 in the csecum, but I have never been able to find convincing 

 proof of this supposition. They bear a great resemblance to 

 the granular oval cells already described as occurring in the 

 coelom, and it is quite possible that they are really derived from 

 this source. 



Never are foreign particles ingested by them, and they do 

 not appear to be at all of a phagocytal nature, although occa- 

 sionally amoeboid. The fine granules in them are evidently an 

 endoplastic product, and I should suggest that the cells secrete 

 a ferment which helps to dissolve the waste material in the 

 sac. The matter in solution would then be carried through the 

 wall of the sac to the nephridium to be excreted. However 

 this may be, it is certain that the cells aggregated in the sac die 

 and undergo degeneration ; this can be clearly seen in sec- 



