746 J. H. ASHWORTH. 



wall. In each of these canals the thin lining of coelomic 

 epithelium may be easily recognised, and coelomic corpuscles 

 may also be found in many of them. Similar canals are 

 present in A. marina (Gamble and Ash worth, 1808, p. 28), 

 in A. grubii, and to a less extent in the other species; 

 but the development of tliese outgrowths of the cocloni 

 reaches its maximum in A. assimilis. They probably act 

 as nutritive, and possibly also as excretory and respiratory 

 channels. There are very few coelomic canals in the pos- 

 terior ]i:irt of tlie animal. The coelomic fluid and corpuscles 

 resemble, as far as can be ascertained in preserved specimens, 

 those of A. marina. 



Nephridia. — There are six pairs of nephridia, the ex- 

 ternal openings of which are slightly posterior to the dorsal 

 ends of the fourth to the ninth neuropodia. The funnels of 

 the first pair of nephridia lie on the anterior face of the 

 third diaphragm. This condition is found again only in 

 A. marina; the first pair of nephridia of other species 

 corresponds in position to the second pair of A. assimilis 

 and A. marina. The dorsal lip of each nephrostome 

 (fig. 17) bears about twelve to fourteen spatulate or triangular 

 ciliated processes attached by their narrower ends. 'J'hese 

 are subdivided distall}', some of the larger ones into five or 

 six. The edge of the ventral lip of the nephrostome is 

 thrown into folds or frills, so that although it agrees in 

 general shape with the ventral lip of the ne])hrostome 

 of the marina section of the genus, the ventral nephro- 

 stomial lip of A. assimilis is quite distinguishable by this 

 peculiar character. This frilling is probably not due to con- 

 traction on killing, as it is not seen in specimens of 

 A. marina, A. claparcdii, and A. cristata which have 

 been killed in a similar manner. 



The nephrostome of the first nephridinm lies on the 

 antei'ior face of the third diaphragm, and is directed an- 

 teriorly, ft is smaller than any of the other nephrostomes, 

 its dorsal lip bears only eight to eleven processes, and the 

 fvilling of the edge of the ventral lip is not so well marked. 



