10 Preface 



. when a course in general limnology was first estab- 

 i rnell University, we have been associated in develop- 



n outline of study for general students and a program of 

 j. The text-book is presented herewith: the 

 ical exercises are reserved for further trial by our own classes; 

 they are still undergoing extensive annual revision. 



The liniitati. >ns of space have been keenly felt in every chapter; 

 ially in the chapter on aquatic organisms. These are so 

 us and so varied that we have had to limit our discussion 

 , ,f t i, , , U ps of considerable size. These we have illustrated 



in the main with photographs of those representatives most 

 commonly met with in the course of our own work. Important 

 S are, in some cases, hardly more than mentioned; the stu- 

 dent will have to go to the reference books cited for further infor- 

 ■'■ m concerning them. The best single work to be consulted 

 in this connection is the American Fresh-water Biology edited by 

 Ward and Whipple and published by John Wiley and Sons. 

 Our bibliography, necessarily brief, includes chiefly American 

 rs. We have cited but a few comprehensive foreign works; 

 the reference lists in these will give the clue to all the others. 



It is the ecologic side of the subject rather than the sys- 

 tematic or morphologic, that we have emphasized. Nowadays 

 there is being put forward a deal of new ecologic terminology 

 t< it which we have not discovered any good use; hence we have 

 omitted it. 



Limnology in America today is in its infancy. The value of 

 its past achievements is just beginning to be appreciated. The 

 fits to come from a more intensive study of water life are 

 just beginning to be disclosed. That there is widespread interest 

 is already manifest in the large number of biological stations at 

 which limnological work is being done. From these and other 

 kindred laboratories much good will come; much new knowledge 

 iter life, and better application of that knowledge to human 

 welfare. 



James G. Needham. 

 J. T. Lloyd. 



