THE ROUND WORMS AND FLAT WORMS 



I2 7 



as they pass backward. Finally the proglottids become 

 constricted off and pass out of the body. The mature 

 proglottids contain fertilized eggs which may be set free 

 either before or after the proglottid is expelled. 



FIG. 105. A human tape-worm Tcenia solium. la, animal with a few 

 segments enlarged at the right showing sex opening on one edge, o; 16, 

 attached end with suckers and circles of hooklets, the latter enlarged at 

 C. (After a Pfurtscheller chart.) 



The eggs do not develop directly into new worms; 

 typically the eggs or embryos are taken into the body 

 of some other animal; here the embryo bores its way 

 through the walls of the intestine and becomes encysted 

 in some part of the body, forming what is called a bladder 

 worm (cysticercus or cysticercoid) . In this state the worm 



