UNSEGMENTED WORMS. 

 FIG. 91. 



>r -T- r- 



CDO 



700 



D 



FIG. 91. Diagram showing some stages in the life history of the Tapeworm (Tcenid). 



A, Cysticercus or Bladderworm stage, before the " head " protrudes from the bladder; 



B, same, later stage; C, Strobila, or chain of proglottides, many being omitted; D, 

 embryo, such as fill the uterus of the mature proglottides. It is protected by a shell. 

 b, bladder; ex., excretory canals"; g, genital pore; h, head or scolex provided with hooks 

 and suckers (s) ; u, uterus in a mature posterior proglottis; z, zone of budding or seg- 

 ment formation. The numerals show the approximate number of the segments, reckon- 

 ing from the front. Not more than 5 per cent, of real length of the chain is 

 represented. 



Questions on the figure. What arguments do you find from the 

 figure for considering the strobila an individual? What for considering it 

 a colony? Where does non-sexual reproduction occur? Where sexual? 

 Seek figures of stages between D and A in the reference books. 



