UNSEGMENTED WORMS 



IQ7 



400 



-doom CO3 



D 



PIG. 93. Diagram showing some stages in the life history of the Tapeworm (Tcenia). 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; A, head or scolex provided with hooks and suckers (5); , uterus in a mature posterior pro- 

 glottis; s, zone of budding or segment formation. The numerals show the approximate number of 

 the segments, reckoning from the front. Not more than 5 per cent, of real length of the chain 

 is represented. 



Questions on the figures. 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. 



