SOME POINTS IN THE ANATOMY OF POLYCH.ETA. 257 



from the spherical mass to open to the exterior on the ventral 

 side of the base of the parapodium. But the internal aperture, 

 the nephrostome, is not a cleft such as Ehlers figures and 

 describes in the wall of the spherical mass. The nephrostome 

 is situated at the end of a simple thin ciliated tube, which 

 projects out from the spherical body at the side opposite to the 

 efferent duct. The nephrostome is funnel shaped, as usual, 

 but the edges of the funnel are produced into numerous finger- 

 like lobes, and from the lobes project a forest of delicate, 

 pellucid, branched processes, the surface of which is beset with 

 extremely long cilia, which move somewhat slowly. The mouth 

 and neck of the funnel seem to be divided longitudinally by a 

 partition. But it is probable that the partition is incomplete. 

 (See figs. 15 and 16.) The somites of Nereis virens are 

 separated by transverse mesenteries, and at the line along 

 which these mesenteries are united to the intestine the latter 

 is considerably dilated, while in the centre of the somite it 

 is contracted. In order to conform to the typical nephridium 

 in its relations, the nephrostome in Nereis virens ought to 

 be on the front side of the septum, behind which the body of 

 the nephridium is situated. AVhether this is so or not I have not 

 been able definitely to ascertain, but I believe it to be so. The 

 septum is close to the front edge of the base of the parapodium, 

 and the nephridium lies slanting across the entrance to the 

 cavity of the parapodium, and above the edge of the ventral 

 band of longitudinal muscles. Thus the distance between the 

 septum and the body of the nephridium is not too great to be 

 bridged by the tube leading from the nephrostome. It is to 

 be noted that the nephridium lies as usual below the oblique 

 muscles. 



Ehlers' observation above quoted, if it were perfectly accu- 

 rate, would prove beyond a doubt that the nephridia in 

 Nereis virens serve to convey the sexual products, or at 

 least the ova, to the exterior. But that observation is in con- 

 tradiction to all the evidence that has come under my notice. 

 The breeding habits of the Nereidae still remain in some 

 particulars mysterious, but it seems clear that the worms of 



