STRUOTUEE OP EARTHWOEM ALLIED TO NEMEETODRILUS. 565 



atrium. Perrier, who was the first to make known the struc- 

 ture of Eudrilus, described the vasa deferentia as opening 

 into a pouch, into which also opened the atrium, regarded by 

 him as the equivalent of the prostate of other earthworms. 

 It is so figured in his memoir (10, pi. ii, fig. 26). I myself 

 showed that, unless we were dealing with different forms, this 

 description was incorrect ; in specimens of Eudrilus coming 

 from several distinct localities I found that the vasa deferentia 

 opened into the structure that had been termed prostate. This 

 glandular tube, I pointed out, was itself divided into two 

 separate tubes by a longitudinal septum not visible or hardly 

 visible externally. Into the longer of the two tubes, at a point 

 corresponding with the apex of the shorter compartment, open 

 the vasa deferentia, each by its own orifice. The structure of 

 Eudrilus has been recently reinvestigated by Dr. Horst (7), 

 who gives a diagram (7, p. 6) agreeing with my figure (15, pi. 

 xxxiii, fig. 15), and remarks that '^ I'appareil genital male est 

 exactement conforme a la description detaillee quiM. Beddard 

 a publiee de cet organe.'^ 



In Teleudrilus Rosa describes the opening of the vasa 

 deferentia into the atrium not far from the anterior extremity 

 of the latter, i. e. not far from their point of opening on to 

 the exterior. The same thing occurs in Heliodrilus 

 and Hyperiodrilus ; in Nemertodrilus the communica- 

 tion between atrium and vasa deferentia takes place, as it 

 apparently does in Teleudrilus, not far from the external 

 aperture of the former. 



In Libyodrilus the arrangement is very interesting. On 

 a dissection of the worm I could not follow the course of the 

 vasa deferentia beyond the point of opening of the atrium ; 

 this was due to the fact that the two tubes, which retain their 

 distinctness though they are in very close juxtaposition, at 

 that point perforate the muscular tissue of the atrium; they 

 pass up, at first within the thickness of the muscular tissue, and 

 later within the epithelium, to nearly the summit of the atrium. 

 At this point they open into its lumen by a common orifice ; 

 the two vasa deferentia unite just at the orifice ; the cilia are 



