•Js| MR FRANK E. BEDDARD 



no connection whatever with the spermatozoa. These nuclei (fig. 16, n.) bear the closest 

 possible resemblance to the nuclei of the peritoneal cells, but how they have managed to 

 get into the sac in question is unintelligible to me. There is, of course, no lining of 

 peritoneum to the circumatrial space, since it is simply caused by the separation between 

 the muscular layer and the epithelium. There is no doubt, however, that they are merely 

 nuclei, and not cells. The muscular coat surrounds the convoluted portion of the atrium 

 and the greater part of the vas deferens, which lies coiled up in the same cavity. Fig. 32 

 represents a longitudinal section through the space which surrounds the atrium, near to 

 the periphery. The section, therefore, does not show the convolutions of the atrium or 

 the vas deferens. The space is seen to be filled with spermatozoa and the mysterious 

 nuclei already referred to. The section happens to have been cut rather obliquely, and in 

 consequence the muscular coat is partly shown in longitudinal section. A more highly 

 magnified section through the muscular layer is illustrated in fig. 33, which shows the single 

 layer of circular muscular fibres in the membrane which separates them from the space. 



In many Oligochseta the vas deferens is enclosed for a greater or less extent within the 

 sperm sac — for example, in Pelodrilus, to be described presently. But in Phreoclrilus there 

 appears to be no question of a sperm sac surrounding the vas deferens. The space which 

 I have described is simply due to the separation between the muscular coat of the atrium 

 and its epithelial lining. The only other type which I can compare with Phreodrilus 

 is Eclipidrilus — a most remarkable genus of Lumbriculidse which has been made known 

 by Eisen. Eisen's description of the organs in question runs as follows [3, p. 6] : — " The 

 efferent ducts are two, of enormous size, occupying the segments IX-XIV. The exterior 

 porus of the duct is situated in the IXth segment, just behind the ventral spines. Each 

 efferent duct consists of two large, rather cylindrical, saclike ducts of nearly equal size, which 

 at the extremities are connected by a narrow, short tube of the same general structure as 

 the rest of the organ, except being surrounded by spiral muscles. The interior extremity 

 of the ducts is free, suspended in the perigastric cavity of the body, but the exterior 

 extremity is, as usual, attached to the body wall, and a part of it projects beyond the 

 same, forming a retractile exterior penis proper. The longest of the two bags, which con- 

 stitute the efferent duct, is the one directly connected with the body wall, and is nearer 

 its interior end, furnished with three very minute circular openings, through which the 

 spermatozoa evidently enter. 



" Inside, and freely suspended within this exterior duct, we find another interior one, 

 of very much the same form and size as the former, only it is somewhat shorter, its exterior 

 extremity being free and not attached to the body wall, nor being able to be projected 

 through the same. This extremity is furnished with a large circular opening. The 

 inner extremity of this interior duct ends blindly, and is always full of spermatozoa, and 

 serves accordingly as a true seminal vesicle, in which the spermatozoa are stored before 

 they are ejected through the sexual porus. 



" The exterior duct consists of at least three different layers — one exterior epithelial 

 layer ; one middle layer, much thicker than the others, consisting of heavy longitudinal 



