FLATWORMS 



Hooks 



Tail 



Fig. 11.21. Immature stashes in the life cvcle of the broad tapeworm or fish tapeworm, 

 Diphyllohothmm /alum. A, free-swimming, ciUated coracidium larvae, which is ingested by 

 a small crustacean such as Cyclops. B, immature, and C, mature procercoid, developing from 

 the hexacanth in the bodv of the crustacean. /), plcrocercoid, which develops in muscles, 

 liver, spleen, or coelom of a fish which has eaten an infected Cyclops. The plerocercoid trans- 

 forms into the mature, segmented tapeworm in the intestine of the final host, a fish-eatmg 

 mammal, after being ingested. (Redrawn, after Rosen, from L. H. Hyman, The Invertebrates: 

 Platyhelrmnlhes and Rhynchocoela, copyright 1951 by McGraw-Hill Book Co., Inc., printed by 

 permission.) 



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