THE NEPHRIDIA OF THE POLYOHiETA. 73? 



end is a single long flagellum, which passes far down the 

 nephridial canal ; the movements of the flagellum are such 

 as to propel liquid down the tube towards the external pore. 



In the majority of cases the cell-body hangs freely in the 

 coelom, supported at the tip of the tube (figs. 11 and 14). 

 The solenocytes then generally become grouped together for 

 mutual support (Part II, fig. 14) ; or the cell-bodies may even 

 be fused into large masses, as in the Alciopids, the individual 

 cell-outlines being lost (figs. 2 and 9). In other cases the 

 cell-body is bent round so as to rest on the surface of the 

 nephridium, an elongated neck connecting it with the distal 

 end of its tube (Part I, fig. 26 ; Part II, fig. 9 ; and this 

 Part, fig. 13). Such cells are usually joined together in 

 pairs, more or less fused. 



The protoplasm of the solenocytes is generally finely 

 granular, occasionally with refringent globules (Phyllo- 

 doce paretti, fig. 14) ; but, as a rule, singularly free from 

 concretions or granules of excretory matter. Indeed, ex- 

 periments seem to show that they are not concerned with the 

 excretion of such waste substances (Part II, p. 452). Often 

 fine, irregular, probably amoeboid processes are given olf from 

 the cell-body (Part II, fig. 4), or from its neck (Part 1, fig. 26). 



The distribution of the solenocytes varies considerably. 

 In Vanadis (fig. 1), where the nephridium is unbranched, 

 they are placed in bunches along the anterior third of its 

 course. In Alciope cantrainii (fig. 3), and Phyllodoce 

 paretti (fig. 14) they are grouped only at, or near the tips 

 of the branches of the nephridial canal. JN'ephthys (Part I, 

 fig, 26), and most Phyllodocids in which the nephridium is 

 branched, have the solenocytes ranged in regular rows 

 facing each other, so to speak, along the whole length of the 

 branches. On the contrary, in Glycera, where the nephri- 

 dium spreads out in a flattened mass, they are irregularly 

 scattered in small groups over its coelomic surface (Part II, 

 figs. 14, and 29). Intermediate forms between these ex- 

 tremes are also found. 



Sometimes cilia are developed in the Phyllodocidge close to 



