MODE OF CONNECTION OE THE SEGMENTS. 



431 



Fig. 245. 



Fig. 244. 



be compared to a joint, the anterior portion of each segment iitting 

 into the preceding one like the head of a bone into its socket. "We 

 have already noted the histological peculiarities of this connection 

 (p. 293). Posteriorly the re- 

 lative size of this connecting 

 portion decreases, and that the 

 more conspicuously as the 

 joints increase in size, until 

 finally in the free proglottides it 

 becomes hardly distinguishable. 



We need hardly specially 

 mention that the boundaries of 

 the segments are not to be 

 confused with the transverse 

 furrows which traverse the sur- 

 face, especially in the much 

 contracted condition. It is 

 indeed only in regard to the 

 short somewhat less developed 

 anterior joints that this con- 

 fusion is possible, for posteriorly 

 the projecting borders of the 

 joints (which are of considerable 

 length, of 0'5 mm. or more), 

 render any such mistake im- 

 possible. At first the segments 

 exhibit only a single transverse 

 furrow, which runs across about 

 the middle, and can be followed 

 into the developing porus genitalis ; afterwards, when the joints 

 become longer, the number of these furrows increases, until they 

 finally disappear in consequence of the longitudinal elongation. 



The Development of Sexual Organs, as well as that of other parts 

 of the body, is associated with the increase in size of the segments in 

 a manner to which we have already alluded. It is more than a 

 mere temporal relation that obtains between the two processes. The 

 formation and development of the sexual organs have a most un- 

 mistakeable influence on the form of the joints and of the whole chain. 

 This is most evident in connection with the specially long or extended 

 joints, which owe their particular shape in great part to processes 

 occurring within the uterus, and essentially amounting to this, that 

 the eggs, with their maturity, attain at the same time their maximum 

 size, and then collect principally in the median longitudinal stem. 

 Digitized by Microsoft® 



Fig. 244. — Head of T. saginaia in a state of 

 contraction. ( x 8.) 



Fig. 245. — Longitudinal section through T. 

 saginata (a young chain). ( x 25. ) 



