8 MR FRANK E. BEDDARD ON THE 



evidence that the atrium, like the spermatheca, does not trace its muscular layer to an 

 invagination of the body-wall muscle, but that these are formed by a differentiation of 

 peritoneum. This view is not in accord with Vejdovsky's figures [4, pi. x. figs. 1, 2] of 

 the developing atrium of Tubifex. The view that the atrium is immature, and not 

 structurally different from that of the other specimen, is confirmed by the fact that the 

 genital ducts are only represented by their funnel; the vasa deferentia and the distal 

 portions of the oviducts were not visible in my sections. 



Absence of Penial Setce at Atrial Pore. — The atrial pore is situated at the junction 

 of the Xth and Xlth segments; the atrium, however, distinctly belongs to segment X, 

 and not to segment XL It will be seen from fig. 8 that the dissepiment which separates 

 segments X-XI, arises on the posterior side of the atrium; this being the case, the atrium 

 may be spoken of as opening behind the setae of segment X. and not in front of the seta? 

 of segment XI; it is therefore the setae of the Xth segment that we should expect to find 

 modified, if any ; but perhaps as the male pore is not definitely related to either pair of 

 setae, and is situated so far away from them, we should not on a priori grounds expect to 

 find either pair modified. At any rate the fact is that there appears to be no modifica- 

 tion to form penial setce. The fact, however, is put forward with due reservation as to its 

 being characteristic of the species, since the specimen is perhaps not fully mature. 



Sperm Sacs. — As I have already described, there are a pair of sperm sacs, which in 

 some specimens would seem to lie in segment IX, in others in segment X ; in both cases 

 they are attached to the intersegmental septum between IX and X. In many specimens 

 which I dissected the sperm sacs appeared to be traversed by the intersegmental septum, 

 i.e., to lie in both segments TX and X; in longitudinal section of one individual, this also 

 appeared to be the case. This specimen happened to be the most poorly preserved, and as 

 in two other cases the sperm sac was either with IXth or Xth segment, I am inclined to 

 believe that the appearances seen in the dissection are simply due to the bulging of the 

 septum. The cavity of the sperm sac is simple — i.e., it is not divided by trabeculae ; in 

 this it resembles the sperm sacs of the lower Oligochaeta ; each sperm sac encloses the 

 testis and vas deferens funnel of its own side. 



Oviduct. — I have nothing to say about the ovary, as I have been entirely unable to 

 discover the least trace of this organ ; it lies, however, probably in segment XL In any 

 case, the oviduct opens into this segment ; in two out of the three specimens, which I 

 studied by means of longitudinal sections, I discovered an unmistakable oviduct. In 

 one specimen I have already figured and described this organ [4], the figure being largely 

 a " restoration," as I could not find the entire organ, but only a portion — in fact, only the 

 coelomic funnel. It appeared to me as if the entire oviduct lay in the Xlth segment ; if 

 this be so — but I cannot be certain about it — there is a curious resemblance to the very 

 anomalous form Plutellus heteroporus [Perrier, 11]. In another specimen the oviducts 

 had not this position ; they opened into the cavity of the Xlth segment, by a funnel 

 which was closely attached to the dissepiment dividing this from the Xllth segment. I 

 did not succeed in following the oviduct to its external pore ; indeed, I do not think that 



