838 PROF. G. C. BOURA^E OX THE [Nox. 17,, 



there is no communication between the anterior ends of the 

 glandular and non-glandular parts. The exception is shown in 

 fig. 19, representing part of a horizontal section through Septaria 

 depressa. In this the tei-minal portion of the non-glandular part 

 is seen to communicate with the glandular part by a small but 

 perfectly distinct orifice in the vicinity of the renal aperture of 

 the reno-j)ericardial duct. I can find no trace of such an orifice 

 in ^S'. hougcdnvillei , but it occui'S in several other ISTeiitida?. It is 

 not an accidental rent in the wall, the epithelium passing in 

 unbroken continuity round the lips of the orifice. 



It is now so generally luiderstood that the kidney of the 

 Neritidfe is the post-torsional left, that it is not necessary for me 

 to insist upon the further evidence in support of this opinion 

 derivable from the facts just mentioned. But it is perhaj^s 

 necessary to allude to the question as Fleure (17) in a compara- 

 tively recent paper has attempted to prove that the single kidney 

 of the ISTeritidse and Pectinibranchia is the left post-torsional 

 and corresjDonds with the large functional left kidney of most 

 Rhipidoglossa, Unfortunately for his argument his paper is 

 followed by that of Miss Drummond (13), in which the fact 

 previously insisted on by von Erlanger (14) is placed bej^ond all 

 doubt, namely that the existing kidney of Paludina (and 

 presumably of other Pectinibranchs) is the post-torsional left.. 

 The rudiment of the post-torsional right kidney becomes converted 

 into the genital duct in the course of embryonic development 

 It is clear, from the presence of the oviduco-coelomic funnel, that 

 the same thing has happened in the Keritidfe. 



The Generative Organs. 



Gilson (18) was the first to give an intelligilile account of the 

 female generative organs of XeritinafluviatiUs, and their structure 

 was subsequently worked out in great detail by his pupil Lenssen. 

 More lately Thiele has described these organs in several species of 

 ISI^eritidfe, including Septaria {Xavicellci) parva and suborhicidaris. 

 A further desciiption would therefore seem superfluous, were it 

 not that Septaria dififers in some not unimportant particulars 

 from Reritina, and Thiele's account of the former genus is little 

 more thaia a brief note, omitting histological detail, and, moreover 

 defective in at least one very important particular. Moreover, as 

 a result of a comparison of Lenssen's and Thiele's work with my 

 own and of an attempt to homologize the difi^erent cavities, ducts, 

 and glands in the different forms that I have examined, I have 

 come to conclusions somewhat difl^erent from those of the two 

 authors named, and have to suggest a new nomenclature for the 

 different parts. Gilson and Lenssen have shown that the female 

 ducts of A^eritina Jiuviatilis are diaulic ; Thiele has made the same 

 statement for Merita and Septaria. A reference to the diagram 

 (fig. 3) will show that the female ducts of Septaria are triaulic 

 There is the large ovipository aperture {Ov.ap>.), through which the^ 



