370 LEWIS HENEi: GOUGH. 



to form the vagina advancing in their development perhaps 

 somewhat more rapidly than those from which the cirrus 

 arises. The central core is at first solid, at this stage it cuts 

 itself off from the surrounding cells by the formation of a 

 basal membrane. The cavity arises by the cells separating 

 in the middle of the epithelial cord. At this stage we find 

 the vagina lined with an epithelium ; later on the cells of 

 the epithelium atrophy and their nuclei disappear. The 

 fully developed vagina (fig. 45) is lined with fine cilia, all 

 pointing away from the pore ; it is surrounded by a sheath 

 of large cells, with round, dai'k-staining nuclei. The 

 plasma of these cells does not stain ; their membranes are, 

 however, very distinct. In shape, the cells are prismatic, 

 with all the sides delimited by planes, tiie ends of the cells 

 bordering on the parenchym generally forming pyramids. 

 These cells surround the vagina in a single layer; their 

 function may be glandular (?), and they certainly help to give 

 greater rigidity to the vagina. 



The female sexual canals, spermiduct, oviduct, uterine 

 duct, canalis seniinalis and the receptaculum seminis all arise 

 as solid cords of epithelial cells, which, after having produced 

 a basal membrane, become hollow. As is the case with the 

 vagina, the epithelium atrophies, and finally disappears. 

 Oviduct, canalis seminalis and uterine duct are, when com- 

 pletely developed, lined with cilia. The receptaculum 

 seminis is not a simple dilation of the spermiduct due to the 

 action of the contents, but arises out of a clump of cells which 

 already show the final shape of the organ. 



The ovarium forms at a very early stage a clump of darker 

 staining cells near the middle of the medullary layer. It is 

 remarkable, when fully developed, as compared with the 

 ovaries of other cestodes, on account of its compactness, and 

 also by reason of the fewness of the oocytes produced. The 

 ovaiy is bean- or kidnev-slmped, the oviduct inserting in a 

 depression of its dorsal side ; it consists of a number of lobes, 

 separated from each other by septa (fig. 41) ; the lobes are all 

 enclosed bv a common outer membrane. The siny-le lobes do 



