310 Proceedings of the Royal Physical Society. 



face of its ovigerous sac The ova (fig. 6) are enclosed in 

 the sac, and are arranged in a racemose manner, enveloped 

 in a very delicate membrane. 



The internal ovaries (figs. 2, 3, & 3', h) are situated pos- 

 teriorly to the peduncle. They constitute an oval, flattened, 

 pulpy mass, dividing the cavity of the parasite into two 

 compartments ; they are attached by the centre of their pos- 

 terior margin to the left wall of the ovario-branchial orifice ; 

 and also, as previously mentioned, by the septum which 

 runs along the left side of the sac, they are connected to the 

 corium (fig. 2 g). In the many specimens examined, I have 

 always found a small tubercle (figs. 2 & 3 o), with a minute 

 and apparently horny speck on its summit, placed on both 

 surfaces (figs. 3 & 3", 6) of the body of the ovaries lying op- 

 posite to one another, a little to the left of the centre of its 

 posterior margin. On removing the little speck of horny 

 matter, a depression is seen in the centre of the tubercle, 

 apparently communicating with the substance of the ovaries. 

 May not these structures be the orifices of the oviducts, 

 closed by a temporary secretion of horny matter till the brood 

 of ova in the ovigerous sac has attained its full develop- 

 ment ? This view of the nature of these tubercles has sug- 

 gested itself to me from the difficulty of accounting for the 

 passage of the ova into the ovigerous sac. The fact that the 

 ova found on the external surface of the ovaries are always 

 more fully developed than those further removed from the 

 surface suggests another view of the subject, — viz., that they 

 are developed in successive layers, and thus constitute the 

 ovigerous lamellae. 



Situated immediately posterior to the peduncle, is a well- 

 defined cavity, lined by a special membrane, and containing 

 two oval-shaped bodies (b) placed side by side. These pel- 

 lucid sacs (figs. 7 and 8) contain in their cavities peculiarly 

 shaped bodies (c), and are provided with convoluted ducts 

 (a). The ducts appear to pass towards the right side of the 

 parasite (figs. 3 and 3', h) along the anterior margin of the 

 ovaries, where they unite and become lost. From the close 

 relation of their ducts to the ovaries, it has all along appeared 

 to me that these vesicles probably play an important part 



