170 



METAZOAN PHYLA 



possess hundreds of proglottids and which may reach a length of many 



feet. 



197. Metabolism. — The steps in metabohsm in a free-hving flatworm, 

 as illustrated in a planarian, have been seen to be not greatly different 

 in general character from those in the coelenterates. It should be noted 



/3co/ez 



Uterus 



Ner\/e 



■Excretory 

 canof/ 



Tesfes 



She// Va//f 



Vasc^efereris -^^^^^ ^^""^^ ^''^^-^ 





Ufervs 



Fig. 83. — The beef tapeworm, Taenia saginata (Goeze). A, the whole tapeworm, 

 with many portions omitted, to illustrate the change in the form of segments in different 

 parts of the body. {From Leuckart, " Parasiten des Menschen.") X }4- B, scolex and 

 neck in an extended condition. The rostellum bears no hooks and the tapeworm is spoken 

 of as unarmed. {From Leuckart.) X 5. C, proglottid, showing the sex organs. {Also 

 from Leuckart.) X 7. D, ripe proglottid, showing the uteius distended with eggs. X 6. 



that though parasitism in the case of the tapeworm has resulted in the 

 disappearance of the digestive system and the absence of the processes 

 of ingestion, digestion, and egestion, all of the other processes in metabo- 

 lism still remain. Absorption occurs over the surface of the body; 

 circulation is from cell to cell; assimilation and dissimilation, secretion, 



