146 



PLATYHELMINTHES. 



Fig. 



79. — Head of T^nia 

 Solium. 



(After Leuckart.) 



the sperms are stored. It communicates with the exterior 



by a vagina, opening close to the penis. 



Eggs pass down the ovi- 

 duct, are fertiUsed by sperms 

 from the seminal vesicle, 

 receive yolk from the yolk- 

 glands and a shell from the 

 shell-gland, and then pass into 

 the uterus. Here they ac- 

 cumulate in enormous num- 

 bers, and a "ripe" proglottis 

 contains a large branching 

 uterus with eggs ; the remain- 

 der of the sexual organs have 

 atrophied. The eggs are at 

 first surrounded by an oval 

 vitelline membrane filled with 

 /_. \ albumen, but later this ruptures 



^ fc: — < and the egg has merely a thick 



B d) '''^"e^: shell. 



HP 5 The ripe proglottides are 



shed one by one and pass to 

 the exterior. The eggs are set 

 free in millions on introduction 

 of the proglottis into the stomach of a pig. The embryo is 

 spherical and has three pairs of hooks. By these, combined 



Fig. 80. — Transverse Section of a Proglottis of T^nia. 



(After Shipley.) 

 Uterus. Ovary. >^ 



\ I Testis. § tj T3 



Note the ring of hooks on the 

 rostrum, the four suckers, and the 

 commencing proglottides. 



^ficj 



w 



m 





Longitudinal 

 Muscles. 



Oviduct. 



Ectoderm. 



