ON TWO NEW GENERA OF AQUATIC OLIGOCH^ETA. 285 



muscles ; and one interior membranous layer, which at the exterior extremity is separated 

 from the two former ones, and forms by itself a pellucid membranous penis at times 

 found projected through the sexual porus. The two exterior ones of these layers connect 

 directly with the body wall, of which they seem to be a mere continuation. This 

 structure of the exterior duct is the same throughout the organ, except at the narrow 

 tube, which connects the two sacs (the seminal vesicle and the atrium), which former is 

 surrounded by numerous spiral muscles very similar to those found in Camptodrilus. 



" If we therefore consider the course a spermatozoon can take, after having escaped 

 from the testes, we find that the efferent duct is most admirably adapted to the purpose 

 of transmitting and storing spermatozoa. A spermatozoon after having entered the 

 efferent duct, through one of the three small circular openings, passes down the exterior 

 duct towards the sexual porus, but is on its way intercepted by the exterior opening of 

 the inner duct, and attracted by the ciliated epithelium of its inner surface, ascends 

 through the exterior part of the duct up through the narrow tube, and is finally lodged in 

 the seminal vesicle, and is here stored until of future use. The spiral muscles round the 

 narrow tube, which can easily be contracted, serve evidently to keep the spermatozoa in 

 the seminal vesicle, and prevent them from escaping in undue time. From the form and 

 free suspension of the inner duct, it may easily be seen that its free exterior extremity 

 can be considerably extended clear down to the penis proper at the moment of copulation." 



The account given by Eisen is in some respects incomplete, owing to the fact that his 

 investigations were made upon the living worm. It appears, however, that in Ecli- 

 ■pidrilus the vas deferens and atrium is entirely surrounded by a sac, which is of a 

 muscular nature, and may possibly be the exact equivalent of the sac which has been 

 described in this paper in Phreodrilus. 



But Eisen has not described in Eclipidrilus any funnel such as I have described in 

 Phreodrilus ; on the other hand, he has figured three ciliated apertures leading directly 

 from the body cavity into the circumatrial space. Since making myself acquainted with 

 Eisen's very interesting paper, I have carefully examined my sections, with a view to 

 discovering if any apertures of this nature exist in Phreodrilus. I cannot, however, 

 find anything of the kind, and the difficulty of understanding how the spermatozoa get 

 into the space which surrounds the atrium, and how the spermatozoa get to the exterior, 

 is still for me unsolved. 



The male efferent apparatus of Phreodrilus thus differs in many details from that 

 of any other genus of Oligochseta. It may present points of agreement with Ecli- 

 pidrilus, but I am inclined to agree with Vejdovsky when he says that the data 

 given by Eisen require confirmation, as the facts described are so very extraordinary. 

 Nevertheless the account given by Eisen, and quoted in full above, is clear and agrees 

 plainly with his figures. As to Phreodrilus, in the first place, the great length of the 

 atrium coiled up itself several times is peculiar, at any rate among the aquatic 

 Oligochseta. The absence of any structure comparable to a penis removes Phreodrilus 



