FRESH-WATER 

 BIOLOGY 



BY 

 The Late HENRY BALDWIN WARD 



Emeritus Professor of Zoology in the University of Illinois, Special 

 Investigator for the United States Bureau of Fisheries, Etc. 



The Late GEORGE CHANDLER WHIPPLE 



Formerly Professor of Sanitary Engineering in Harvard University and 

 THE Massachusetts Institute of Technology 



WITH THE COLLABORATION OF A STAFF 

 OF SPECIALISTS 



NEW YORK 



JOHN WILEY & SONS, Inc. 



London: CHAPMAN & HALL, Limited 



