STRUCTURE OP EARTHWORM ALLIED TO NEMERTODRILUS. 579 



each side a sort of funnel, the inferior part of which communi- 

 cates with one of the pores on the 14th ring. Although the 

 ovaries could not be found, I suppose that this funnel may- 

 function as an oviduct." 



In Nemertodrilus the spermathecal sac is in a condition 

 of arrested development ; it resembles to a certain extent the 

 early stages in the development of Libyodrilus, but secondary 

 modifications — in the complicated fringe which surrounds the 

 pores on Segment 13 — appear to prevent their performing the 

 function of an oviduct. It would be very interesting to have 

 some information about the development of the large sacs in 

 Nemertodrilus, particularly as to whether they originally 

 communicate with the egg-sacs or not. 



VI. Homologies of the Reproductive Organs in Eudrilidse. 



The homologies of the different parts of the reproductive 

 system in Eudrilidae are by no means easy to decipher. 



It is possible, however, to attack the problems with greater 

 confidence in view of the developmental facts that I have been 

 able to bring forward. Hitherto nothing but the adult struc- 

 ture was known, and that in certain cases evidently imperfectly. 

 It is clear that in many points the Eudrilidse differ greatly from 

 all other earthworms ; and I think that this paper rather 

 accentuates the differences than removes them. 



On the other hand, I have been able to show that at a certain 

 stage of development the female reproductive system closely 

 resembles that of more normal genera; the special peculiarities 

 of the Eudrilidse are a later formation ; this argues for the 

 isolated position of the group, which I have elsewhere urged, 

 but not for its primitive characters ; the reproductive system 

 must be looked upon as much modified from that of other 

 earthworms. 



It seems fairly clear that the large unpaired sacs which exist 

 in the genera Heliodrilus, Hyperiodrilus, Stuhlmannia, 

 Polytoreutus, Paradrilus, Preussia, Nemertodrilus, 

 and Libyodrilus correspond in every case. But they are in 



