THE PLANKTON OF THE LAKES. 



By E, A. BiRGB 

 President, University of Wisconsin, Madison, Wis. 



I shall speak this morning about the plankton of inland 

 lakes — that assemblage of minute plants and animals which float 

 in the open waters of the lake and which constitute a great part 

 of the fundamental food for all higher aquatic organisms. The 

 Wisconsin Geological and Natural History Survey has for years 

 devoted much attention to the investigation of this complex sub- 

 ject, and I have here an early copy of a report which covers a 

 part of that work. It deals with the quantity and the chemical 

 composition of the plankton of Lake Mendota and adjacent lakes. 



As the older members of this Society know, I have been 

 much interested in the study of limnology and for a good many 

 years I took an active part in it. In recent years I have had 

 other duties and most of the work for our reports has been done 

 by Mr. C. Juday, who has given all of his time to it since 1905. 

 I had expected him to do much of the talking today, but he is 

 necessarily absent from the cit3\ I am very sorry that you should 

 lose the advantage of his great knowledge of the subject. 



The field work for this report was carried on from 1911 to 

 1917, and was executed upon a large scale. We secured the plank- 

 ton from large quantities of water in such amounts that chemical 

 analyses could be made. Food analyses were also made so that 

 some notion could be reached not only of the quantity of the 

 plankton but also of its value as food. All of these results are 

 summarized in this report, which is very definitely scientific in 

 character, and is for reference rather than for general reading. ^ 



A very good and more popular account may be found in the 

 report of the New York Conservation Commission on Lake 

 George. This gives an excellent general account of the plankton 

 and its relation to the fish besides much other information on 

 the lake, ^ 



1 The Inland Lakes of Wisconsin. The Planliton: Its Quantity and Chemical 

 Composition. E. A. Birge and C. Juday. 1922. 



" A Biological Survey of Lake George. J. G. Needham, C. Juday, E. Morse, 

 C. K. Sibley and J. W. Titcomb. 1922. 



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