STRUCTURE OF EARTHWORM ALLIED TO NEMERTODRILUS. 571 



of the genital region of the worm the oviduct is seen to be 

 ensheathed in a tolerably thick muscular coat, as is the case 

 with all other Eudrilidse. In the young the oviduct is con- 

 nected both with the interior of Segment 13 and with the egg- 

 sac in the way that is generally found in earthworms. In the 

 adult worm the large spermathecal sac nearly fills the 13th 

 segment and encloses the egg-sac, though, as has been already 

 said, there is no communication between the two. Near to its 

 opening into the egg-sac the oviduct is invested with a specially 

 thick muscular coat ; it opens into the interior of the egg-sac 

 by a not very extensive funnel ; just before its opening into the 

 egg-sac it gives oflP a narrow branch which passes into the 

 wall of the spermathecal sac, becoming narrower as it proceeds, 

 and ultimately opens into the interior of the sac by a very 

 small aperture. The aperture into the spermathecal sac can- 

 not be of any functional importance, since the ovary is an 

 evanescent organ, and there are no ova to be found in the sac 

 of the adult and nearly adult worm. At the point where the 

 branch of the oviduct opens into the spermathecal sac the 

 walls of the latter are specially thickened, and project into its 

 interior in the form of a rounded pad. The formation of two 

 openings from the originally single aperture is, of course, due to 

 the growth of this spermathecal pouch, which cuts off the open- 

 ing of the egg-sac into the body-cavity, and at the same time 

 that part of the oviducal funnel which opened in the younger 

 stages into the egg-sac. 



V. Description of some Young Stages. 



The youngest individual which I examined was rather more 

 than half an inch in length. I imagine that it could not have 

 long escaped from the cocoon. 



It is quite evident from an examination of this embryo that 

 the present species is hatched in a much more imperfect con- 

 dition than either Lumbricus or Acanthodrilus, the only 

 two genera of whose development we have at present any 

 knowledge. In the embryo of Lumbricus, according to 

 Bergh, the testes and ovaries are present while it is still within 



