ON A CESTODE FROM CESTBACION. 409 



the Avail is tliickei^ and contains a large number of super- 

 ficially situated nuclei. 



The vagina (tigs. 6, 9, and 10, va.) opens into the shallow 

 genital cloaca by a narrow aperture immediately in front of 

 the male aperture. The terminal part is somewhat dilated. 

 From this point it bends round the sac of the penis as a narrow 

 tube, which dilates again to a diameter of about '05 mm., 

 as it runs straight backwards immediately above (i. e. on 

 the dorsal side of) the secondary uterus. When it reaches 

 the region of the ovary it again becomes narrower and more 

 sinuous. Eventually passing backwards on the dorsal side 

 of the isthmus, it becomes somewhat dilated again to form a 

 vesicle, the receptaculum seminis (figs. 6, 7. 9, JO, 11, and 

 12, r. s.). From the rounded posterior end of this a 

 narrow duct, the fertilising duct (/. d.), runs to join the 

 oviduct. 



In the posterior part of its extent the vagina has a thickish 

 muscular wall consisting of external longitudinal and in- 

 ternal cii'cular layers. Intei-nal to this is a cuticle beset 

 with exceedingly minute spinules. External to the muscle is 

 a layer of cells resembling those cells of the oviduct which I 

 have supposed to be myoblasts. Anteriorly the muscular 

 layers become reduced, and longitudinal fibres alone are 

 present. The fertilising duct resembles the oviduct in 

 structure, but the cuticular hairs are absent. In the 

 posterior proglottides of the strobila (fig. 2) all parts of the 

 reproductive apparatus are represented, though neither the 

 male nor the female organs are mature, and there are no 

 eggs in the uterus. The latter has a comparatively narrow 

 lumen surrounded by a thick layer of small cells; its aperture 

 of communication with the primary uterus is already 

 developed. In more anteriorly situated proglottides the 

 uterus is represented by a solid cord of small cells running 

 along on the ventral side of the vagina. 



