172 



adult topevoorrn 



THE RISE OF ANIMAL LIFE 



Fig. 9-13. Life history of the beef tapeworm {Taenis saginata) of man. 



An examination of the proglottid demon- 

 strates the fact that it is almost a complete 

 individual itself. Indeed, the tapeworm is 

 sometimes considered a colony in which 

 each proglottid is an individual, much like 

 the buds in hydra or the polyps in Obelia. 



Besides rudimentary nervous and excre- 

 tory systems it possesses male and female 

 sex organs, which are capable of produc- 

 ing prodigious numbers of sperms and 

 eggs. The testes, numerous and scattered 

 throughout the proglottid, are connected 



