THE NEPHRIDIA OF THE POLYCH^TA. 723 



the large genital funnel surrounds and fuses completely with 

 its inner end, forming a trumpet-shaped ccBlomic funnel. 

 The genital products, collected together by the action of its 

 ciliated surface, pass down into the nephridium, and so to 

 the exterior by the nephridiopore. 



Syllid^ (Part III, p. 708). 



Those segments of Syllids from which genital products are 

 not expelled, the regions, whether sterile or not, in which at 

 all events the generative cells do not reach maturity, possess 

 a simple nephridium. It is a slender tube, opening into the 

 ccelom by a small nephrostome, running backwards through 

 the septum into the next segment, where it reaches the ex- 

 terior on the ventral surface. The canal is ciliated more or 

 less continuously throughout, as in other Polychaetes, and a 

 special bunch of long cilia is borne on the projecting lower 

 lip of the nephrostome. The upper lip is generally repre- 

 sented by a little mass of closely packed cells, which is ap- 

 parently a thickening of the coelomic epithelium, and the 

 rudiment of the genital funnel. In mature specimens of 

 those forms which do not reproduce by budding, and in the 

 ripe buds or reproductive regions of those which do, the 

 genital funnel becomes very much enlarged, extending up 

 the septum on to the body-wall, and surrounding the opening 

 of the nephridium. The original nephrostome is then no 

 longer distinguishable. The canal of the nephridium be- 

 comes much enlarged, and the whole organ functions as a 

 genital duct. 



Amphinomid^ (Part III, p. 712). 



In these woi'ms, of which the genera Euphrosyne and 

 Eurythoe have been studied, the nephridia are provided with 

 a trumpet-shaped funnel opening inwards and backwards. 

 The funnel passes forwards and downwards into the nephri- 

 dium, which is a short, thick, slightly coiled tube, running 

 backwards, and opening to the exterior ventrally by a minute 



