25G J. T. CUNNINGHAM. 



Nereis virens, Sars. 



Claparede did not study the nephridia in the Nereidse. 

 Ehlers 1 has given a description of the organs as he saw them 

 in Nereis cultrifera, Grube, and other species. He says 

 the segmental organ lies close behind the entrance into the 

 cavity of the parapodium, on the inner surface of the ventral 

 body wall, near the lateral border of the ventral muscular band : 

 that it consists of an easily noticed, almost spherical body, 

 and an efferent duct, which runs on the ventral body wall 

 towards the hinder border of the segment, where it opens to 

 the exterior : that the body of the segmental organ in a large 

 epitokous female of N. virens was '189 mm. by "108 mm. in 

 size. In the inside of the body of the organ he states there were a 

 number of clear cavities, which, when the organ was compressed, 

 were discovered to be portions of a continuous convoluted canal 

 which was embedded in the mass of the organ; the inner 

 surface of the walls of this canal was ciliated. On the upper 

 surface of the body of the organ was a slightly curved, cleft-like 

 aperture, with thickened edges, which carried cilia; this cleft 

 was the internal opening of the organ ; on the opposite side of 

 the spherical body the thin efferent duct passed off. Ehlers 

 concludes his description thus : " In support of the view 

 expressed by myself, that the segmental organs serve as 

 efferent ducts for the sexual products, I may point to the fact 

 observed by me that these organs in N. virens contained 

 perfectly mature ova, which were found in the efferent duct of 

 the organ as well as in its body, and that not seldom a single 

 ovum lay in the external aperture." Ehlers gives a figure of 

 an isolated segmental organ which corresponds fairly well with 

 his description. 



But that description is erroneous in one important point. 

 The segmental organ or nephridium in Nereis virens does 

 consist of a somewhat spherical mass composed of a number of 

 glandular ciliated tubes, which probably all form a single 

 convoluted tube, and a straight, thin, efferent duct, passing off 

 1 ( Die Berstenwurmer,' 1864—1868. 



