EXCRETORY ORGAN OP FRESH-WATER POLYZOA. 



845 



presence of certain origans in this region, and also to the peculiar shape 

 of the body itself. 



Woodcut 1. Woodcut 3. 



<'9. 



Woodcut 2. 



Woodcut 4. 





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The exact form and extension of the body -cavity at the upper 

 end of the polypide and its relation with various organs will be best 

 understood by referring to the accompanying woodcuts, which show 

 cross sections of the upper portion of a polypide at the levels indicated 



