446 



GROWTH AND STRUCTURE OF T^)N T IA SAGINATA. 



one side or the other a somewhat broad streak of cellular parenchyma. 

 At first (A) the stripe does not extend laterally beyond the median 

 region of the joint, but gradually it elongates until it finally abuts 



FIG. 252. Development of the efferent generative organs in Tccnia saginata. 



against the lateral. But before this (JB) the median end has thickened, 

 and become a posteriorly directed club-like swelling, which gives 

 the parenchymatous streak a certain resemblance to a pistol. The 

 contour, which was at first somewhat vague, and which made the 

 rudimentary structure look broad and plump, becomes more sharply 

 defined. As the joints increase in size, the length of the paren- 

 chymatous streak increases. It becomes more slender and changes 

 further ((7), since the terminal club-shaped body becomes almost 

 triangular, owing to the elevation of its anterior margin. Some 

 centimetres further on, about 100 joints after the appearance of the 

 first rudiment, this elevation has elongated into a streak, which can 

 be followed up to the anterior wall, and apparently represents the 

 first rudiment of the uterus. In the transverse streak, on the other 

 hand, we have neither the vas deferens merely, nor the vagina, but the 

 common rudiment of both these structures. This can be easily 

 proved, for the borders of the streak become gradually separated, as 

 two strands, by the clearing of the median portion and the thickening 

 of the borders, and these, though sometimes only imperfectly sepa- 

 rated, and still in connection with the mass of the uterus, may be 

 distinctly recognised as vas deferens and vagina. The former is at 

 first quite straight and destitute of a cirrhus-pouch, but that is no 

 more difficult to explain than the absence of the generative cloaca. 

 On the vagina there is sometimes no perceptible opening nor differ- 

 entiation into the various divisions, although the posterior end is 

 thickened like a club, and forms a swelling, which can be sharply dis- 

 tinguished from the adjacent parts of the uterus. 



The next change in the generative organs is the disappearance of 

 the intermediate substance, which has as yet united the vagina and 

 vas deferens together. The two ducts thus become free, and develop 

 independently by the differentiation of the cirrhus-pouch and the 



