TABLE OF CONTENTS 



Page 



List of figures v 



Preface vii 



Introduction 1 



Chapter I. Apparatus, methods and purpose of investigation 7 



Historical 7 



Pumps and net . 9 



Centrifuge 12 



Chemical methods 16 



Purpose of investigation 17 



Chapter II. The net plankton of Lake Mendota 20 



Thermal stratification 20 



Quantity of water and of plankton 23 



Lake Mendota 25 



Organic matter in net plankton 25 



Chemical results 31 



Nitrogen and crude protein 31 



Ether extract 40 



Carbohydrates 42 



Crude fiber 43 



Nitrogen-free extract 44 



Ash 45 



Constituents of ash 52 



Eesults of other investigators 54 



Organisms 55 



Chapter III. The nannoplankton of Lake Mendota 62 



Effect of centrifuging 64 



Quantity of material 66 



Organic matter 67 



Nitrogen and crude protein 70 



Ether extract 75 



Pentosans 79 



Crude fiber 79 



Nitrogen-free extract 80 



Ash 80 



Organisms 83 



Role of bacteria 88 



Chapter IV. The total plankton of Lake Mendota 92 



Variations in quantity 92 



Mean quantity and chemical composition 97 



Total plankton per unit area 98 



Plankton of entire lake 102 



