An elementary text book of fresh-water 

 biology for students 



BY 

 JAMES G. NEEDHAM 



Professor of Limnology in Cornell University 



and 



J. T. LLOYD 



Formerly, Instructor in Limnology in Cornell University 



FORESTA INSTITUTE 



FOR 



MOUNTAIN 

 STUDIES 



c205 FRANKTOWN ROAD 

 CARSON CITY, I^VADA 897W 



THIRD EDITION 



ITHACA ^SOKS^ NEW YORK 



COMSTOCK PUBLISHING COMPANY, INC. 



1937 



