STRUCTURE OF TWO NEW GENERA OF EARTHWORMS. 251 



The receptaculum, or egg-sac, as it may be more simply 

 termed, is of considerable size, and is divided up into numerous 

 compartments, which lodge the developing ova, by trabeculae; 

 it is closely attached to the pericesophageal ccBlomic sac, as 

 shown in the figure (fig. 10), and in all probability opens into 

 it, though I confess to not having been able to find the actual 

 orifice of communication. 



The oviduct is a short, straight tube, which passes directly 

 from its opening into the egg-sac to the external aperture upon 

 Segment 14. It is lined by a columnar ciliated epithelium, 

 and it has strongly developed muscular walls. 



The coelomic sac involving the ovaries, and continuous with 

 the ring round the oesophagus, facilitates the passage of ova 

 from the ovary to the receptaculum and to the oviduct ; but 

 the extension of the sac beyond the limits necessary for that 

 purpose is a little difficult to understand. 



I could not find any spermatozoa in the dorsal sac, nor, for 

 the matter of that, in the spermatheca ; and if impregnation 

 takes place by the bursa copulatrix, there seems to me to be no 

 way by which the spermatozoa could reach the interior of the 

 sac. I could detect no orifice leading from the spermatheca 

 to the sac which involves them, and such a connection seems 

 hardly likely to occur. 



In nearly all the Eudrilidse the ovary is contained in a 

 special coelomic sac, which communicates indirectly with the 

 exterior. The principal exception is Nemertodrilusj but 

 here the reduction in size of the cavity of the 13tli segment 

 seems to guide the ova to the aperture on to the exterior of 

 the body, and there is thus no need of the formation of a special 

 tube (see p. 266). 



The remarkable genitalia of Polytoreutus are perhaps 

 rendered more intelligible by the facts which I have been able 

 to make out inHyperiodrilus. I have little doubt that the 

 median sac, communicating on the one hand with the 

 " spermatheca,'^ and on the other with the oviduct, will prove 

 to be a coelomic space perhaps surrounding the true sperma- 

 theca. It seems to be possible that the female organs of 



