634 



2. In the second part of the communication, the structures are 

 indicated which the authors hold to be the true oviducts. One 

 large band which is seen at the spawning season as a prominent 

 ridge projecting into the calibre of the lower segment of the intes- 

 tinal tube, and two smaller ones, which are traceable from the com- 

 mencement of the intestine down to a point where its upper coils 

 are in close proximity to that part of its lower segment where the 

 former band ends in a club-shaped dilatation, are shown to dis- 

 charge this function. The method of dissection to be adopted for 

 the demonstration of these structures is given at some length, and 

 the following arguments are adduced in support of the view which 

 regards them as oviducts. A fine injection thrown into the largest 

 of the bands in question is seen to pass into the ovary, and is re- 

 cognizable under the microscope as contained within the limitary 

 membrane of its ultimate follicles. Its distribution, therefore, as 

 detectable at once by the naked eye and by the microscope, con- 

 trasts strongly with that of a similar injection thrown in by either of 

 the aquiferous orifices. Secondly : The condition of distention, 

 prominence, and intumescence of this band, coincides with similar 

 conditions in the ovary ; and from an acquaintance with the condi- 

 tion of the branchial marsupium's contents we are enabled always to 

 predict what will be found to be that of this band. Thirdly : At 

 periods when ova are being rapidly secreted by the ovary, ova are 

 to be found at all points within the whole length of these three 

 bands. The double oviduct at the oral and the single at the anal 

 extremity of the Lamellibranchiata, is what our knowledge of their 

 development would lead us to anticipate ; and the close connexion of 

 the principal oviduct with that latter outlet, and with the lower 

 segment of the intestinal tube, brings the anatomy of these bivalve 

 mollusks into exact correspondence with that of higher tribes in the 

 same series. 



What is said of the ovarian secretion and outlets, applies, mutatis 

 mutandis, to the testicular. 



The paper is illustrated by drawings taken from dissections of the 

 common fresh-water muscle, Anodonta Cygnea. 



