8 GUIDE TO THE STUDY 



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 United States and Canada of Clinostomum marginatum, a trematode 

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Walton, A. C, 1929. Studies on some nematodes of North American 

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Ward, H. B., and G. C. Whipple, 1919. "Fresh-water Biology." 



Wenyon, C. M., 1926. "Protozoology," Vol. 2. 



