645 



the spermathecae as in Eudrilus, were covered with a layer of muscles 

 continuous with the investment of the receptaculum as they are in 

 Eiidrihis. The receptacula contained only mature ova surrounded by 

 a few cells serving probably for their nutrition, and Rosa suggests 

 that this is also the case with Eudrilus. I may refer to my figures of 

 the »developing ova« oî Eudrilus^ which do not appear to me to favour 

 any other construction than that they are really developing ova. If the 

 supposed ovary oi Eudrilus is nothing more than a receptacvilum ovo- 

 rum then the organ in question is anomalous by reason of the fact 

 that the ova undergo within it their whole course of development. 

 This has never been described in any earthworm. If however the egg- 

 sacs of StyJaria "^ are the equivalents of the receptacula ovorum the 

 condition of the supposed receptacula of Eudrilus is less anomalous 

 than it would otherwise be ; but, it must be noted, if this comparison 

 be allowed, it is highly probable that the structure which I have termed 

 ovary in Eudrilus is really ovary -|- receptaculum ovorum. This view, 

 as I stated in my former paper, is an extremely probable one ; but it 

 does not affect the anatomical fact that the ovary of Eudrilus is con- 

 tinuous with the oviduct. For the matter of that there is, as Rosa 

 points out, a continuity of ovary and oviduct in Teleudrilus which is 

 equally direct. 



Another difficulty in the way of supposing that the cellular mass 

 with developing ova in segment 14 is really an ovary is its position. 

 The ovaries of segment 1 3 correspond in position to the testes but 

 not to the supposed ovary of segment 14. The difference however is 

 not a very great one and it hardly appears to exist in Teleudrilus judg- 

 iu!.,^ from Rosa's figure (fig. 3); in specimens of Eudrilus it occasionally 

 happened that the position of the ovaries of segment 14 corresponded 

 with those of segment 1 3 ; and seeing that the mesentery separating 

 segments 13 and 14 is very imperfect, the ovaries after becoming sur- 

 rounded by the muscular sac which forms the extremity of the oviduct 

 may easily have shifted in position. The usual difference of position 

 of the ovaries of segment 1 4 from those of segment 1 3 must be in fact 

 largely dependent upon the growth of the spermathecae, to which they 

 are closely attached. 



The passage of the ova from the gonad into the receptaculum in 

 Teleudrilus is of course facilitated by the tube leading directly from the 

 one to the other; in the majority of earthworms it is not easy to under- 

 stand why the ova pass into the receptaculum instead of to the exterior 



6 Journ. Anat. Phys. Oct. 1887. Vejdovsky. 



■7 System u. Morpìiol. d. Oligochaeten. PI. IV Figs. 2, 7. 



