CESTODA. 325 



a Tapeworm commonly found in the dog and cat ; but the glandular 

 organs being double, the outlets are double also, and exist on both 

 lateral edges in each segment. In Taenia mediocanellata from the 

 human species, the common generative depression is situated some way 

 behind the middle of the lateral border of each segment ; in Taenia 

 solium it is nearer to the middle line, whilst in Bothriocephalus latus, 

 which, like the two Tapeworms named, infests the human subject, both 

 sexual orifices are situated on the ventral aspect of the segment. The 

 statement that the male orifice may occur in some cases on the edge, 

 and the female on the surface of a segment appears to be erroneous. 

 A segment with the generative organs in the condition here figured, would 

 be found in either Taenia solium or Taenia mediocanellata, the two 

 common human Tapeworms, at about the 45oth segment counting 

 backwards from the head ; and the segments would assume the ap- 

 pearance given in Figures 3 and 4, after about 200 more segments in 

 Taenia solium, and 360 to 400 in Taenia mediocanellata. 



FIG. 3. Segment of Taenia solium, to show the dendritic outgrowths of the uterus, about 

 twice the natural size; after Leuckart, I.e., p. 387, Fig. 156. 



IN this segment the uterus and its contents have increased and en- 

 croached so much upon the rest of the generative organs, as to have 

 caused their disappearance. In Taenia solium, its dendritic ramifications 

 have a yellowish colour, and contain aggregations of embryos, such as the 

 one figured at 4, enclosed in a hard resistent shell. 



The uterus in the smaller Taeniae enlarges into a simple sac as the ova 

 collect in it In others again it acquires small lateral ampullae. The 

 Taeniae possess no entrance to the uterus other than the vagina and fer- 

 tilising canal. In some Cestoda the uterus possesses an aperture of its own. 

 The ova acquire their shell within the uterus ; the germ segments, forms the 

 proscolex (Fig. 4) and the shell of the embryo. As there is no uterine 

 aperture the embryo shells with the proscolices are set free by the drying 

 up and dehiscence of the proglottis, or rupture of the uterus, or by digestion 

 of the soft tissues when the proglottis is swallowed entire by the host. 



FIG. 4. Embryo or proscolex of an ordinary Taenia, armed, as it is normally in this genus and 

 other Cestoda, with six spines; after Van Beneden, I.e., PI. xxvi. Fig. 27. 



SUCH an embryo as this is about three times the size of a human blood- 

 corpuscle, o'O22-o'oa8 Mm, and when set free from the hard shell, which is 

 not drawn in this figure, by the action of the digestive fluids of its host, it 

 bores and pushes its way from the mucous surface of the stomach either 

 into the blood-vessels, and so passes into the liver, a very common place 

 for the development of the cystic stage, or into the connective tissues. 

 The two spines of the central pair of the three are symmetrical, and, in 



