236 



ZOOLOGY 



SECT. 



(Fig. 184), the uterus, with its contained accumulation of 



becomes so large as to fill the greater part of 

 the interior of the proglottis, the remainder 

 of the reproductive apparatus meanwhile 

 having become absorbed. 



Development. When the ripe progiottides 

 are detached they pass to the exterior with the 

 faeces of the host. For a time they exhibit 

 movements of contraction. The embryos con- 

 tained within the eggs have meantime assumed 

 the form of rounded bodies, each armed with six 

 chitinoid hooks the six-liookcd or hexacanth em- 

 bryo (Fig. 185, A) enclosed within two mem- 

 branes. If the progiottides or the eggs which 

 have escaped from them, should now be taken 

 into the alimentary canal of the Pig, which forms the ordinary 

 second host of the parasite, the hooked embryos, becoming free< I 



Fir;. 184. "Ripe " pro- 

 glottis of Tsenia 

 solinm. (After 

 Leuckart.) 



PIG. 185. Development of Tapeworm. A, hexacanth embryo; B, Proscolex of Tan\ 

 saqinatn; CE, stages in the formation of the sc-olex of the same ; C, the invagination befo 

 the hooks and suckers have become developed; I), after the appearance of the hooks au 

 suckers; #, partly evaginated ; /'. fully evaginated scolex of T. solium with caudal vesicle 

 G, scolex of T. a rrata with remains of the vesicle ; H, young tapeworn of T. *.//?. (Afte 

 Leuckart.) 



from their coverings, bore their way with the aid of their hooks 

 through the wall of the alimentary canal, and reach the voluntary 



