STRUCTURE OF TWO NEW GENERA OF EARTHWOKMS. 260 



are not far removed from those of the more typical Oligo- 

 chseta. 



It is perhaps possible to regard the pores in Nemerto- 

 drilus as the earlier condition. Observations upon the abdo- 

 minal pores and oviducts of certain Ganoids and Teleosteans 

 seemed at one time to indicate that the pores were the 

 primitive structures^ and that a groove in the peritoneum^ 

 converted later into a tube^ connected these pores with their 

 respective gonad. But if Jungersen^ is right in looking upon 

 the oviducts of Teleostei as being after all Miillerian ducts, 

 this view must fall to the ground. Sedgwick^ brings forward 

 many facts towards proving that in Peripatus the genital 

 ducts are coelomic sacs communicating with the exterior by 

 pores. The ovary in Nemertodrilus, closely invested by the 

 ccelom which opens on to the exterior by a pore, is comparable 

 to the gonad and its duct in Peripatus; it is possible, as I 

 have already suggested, that in Eudrilus the oviduct is only 

 a portion of the coelom connected with a pore ; but 1 am more 

 disposed to hold that Nemertodrilus is in these points a 

 degenerate form of Eudrilus; the reduction of the coelom of 

 Segment 13, and the disappearance of the spermathecse bears 

 out this view. 



In any case two pairs of oviducts seem to imply two 

 pairs of ovaries, which are reduced to one by the disappear- 

 ance of the anterior oviducts. And we thus arrive at the 

 normal condition of the female reproductive organs in earth- 

 worms. 



In Teleudrilus the complete disappearance of one pair of 

 oviducts is correlated with the disappearance of the second 

 pair of ovaries. 



In short, the new facts discovered by Dr. Michaelsen lend 

 support to the conclusions which I formulated in the paper 

 referred to above, apart altogether from the question as to the 



' "Beitrage zur Kenntniss der Entwickelung der geschlechtsorgane bei 

 den Knochenfischen," ' Arb, Zool. Zoot. Inst.,' Wiirzburg, 1890. 



^ "A Mouograpli of the Development of Peripatus capensis," 

 ' Studies Morph. Lab. Cambridge,' vol. iv, part 1. 



