FORM OF NEPHRIDIA IN ARENICOLID;E. 



255 



diminish in size. When occasionally there are an unusally large 

 number of them along the blood vessel beyond the angle, the 

 angle of the funnel adjacent to the muscle tends to become the 

 apex of the funnel as in A. cristata, and the mouth shifts so as to 

 more nearly face this angle instead of a side. In such cases the 

 throat of the funnel opens into the body some distance back of 

 the anterior end of the latter. 



The funnel of the nephridium of A. Claparedii (Figs. 7 and 8) 

 is least complicated. If we imagine a simple funnel form with 

 short stem to be flattened and to have one lip pulled out into a 

 triangular protrusion, we may gain a clear idea of the funnel of 

 this species. The apex of the dorsal lip is broadly obtuse ; the 

 ventral lip is straight. The dorsal lip is set with the ciliated plates 

 characteristic of the marina section of the genus which, as Gamble 

 and Ashworth point out, includes the species Claparedii, cristata 



CT? 



c 



FIG. 9. Dorsal view of the first left nephridium of Arenicola ecandata, X 1 S 

 C.P., ciliated processes. D.L., dorsal lip. G. F., gonadial blood vessel. 



FIG. 10. Ventral view of the anterior portion of nephridium (first left) of A. 

 ecaudata, X J 5- V.L., ventral lip. 



and marina. There are ten or twelve of these plates in A. Clap- 

 aredii. The funnel is at the anterior end of the body and its axis 

 is also at right angles to the axis of the body of the nephridium. 

 The funnel of the nephridium of A. ecaudata (Figs. 9 and 10) 

 is reniform in outline with re volute ends as seen from the ventral 

 face. It also is flattened ; the dorsal lip is slightly concave, the 

 ventral lip is deeply indented. The dorsal lip is provided with 

 ten to thirty blunt, at times much branched, finger-like processes ; 



