580 FRANK E. BEDDARD. 



this event not spermathecse^ except in function. A true sper- 

 matheca, as I have shown, exists in Heliodrilus and Hy- 

 pe riodrilus, partly or entirely enclosed by the median sac. 

 In Paradrilus, too, judging from Michaelsen's figure, there 

 is a spermatheca of this kind, but apparently not in some of 

 the other genera; nor is this structure represented in Libyo- 

 drilus. In Libyodrilus the large unpaired sac is 

 obviously a spermatheca in function, for I found 

 sperm in it, but its development shows that it cannot 

 possibly be compared to the spermatheca of, e. g., 

 Lumbricus. It is a mesoblastic pouch which has 

 acquired an external opening; whereas the spermatheca 

 of Lumbricus are known, through the investigation of Bergh, 

 to be purely epidermic involutions. The homologue of the 

 spermatheca of Heliodrilus and Hy periodrilus in Libyo- 

 drilus appears to be the orifice only of the mesoblastic sac. 

 In this connection the structure of Nemertodrilus as 

 described by Michaelsen is of great interest. He has described 

 (3), and I have been able (1) to entirely confirm his descrip- 

 tion, a pair of apertures in Segment 13 which lead into the 

 interior of that segment ; they have no connections with the 

 sacs extending backwards from Septum 13 — 14, but Michaelsen 

 has suggested that they represent the orifices of those sacs ; I 

 am now of opinion that this suggestion is perfectly correct. 

 So far Nemertodrilus appears to be a degenerate form, and 

 other structural facts confirm that view. It is a little difiicult 

 to understand the arrangement of the various organs in 

 Preussia, since Dr. Michaelsen was unable, through being 

 obliged to respect museum specimens, to make out the relation 

 of the ovaries. 



The following is Michaelsen's description of the parts in 

 question : I think it worth while to quote it in full, as the 

 journal in which it is contained may not be accessible every- 

 where. 



" Der weibliche Geschlechtsapparat zeigt wieder eine neue 

 Modifikation der eigenartigen Verwachsung, wie sie fiir die 

 Teleudrilen charakteristisch ist. Die ventral median OfFnuug 



