CONTENTS. 



PAGE. 



Introduction i_i 7 



Distribution of Collections by Months (Table) 4 



Methods 5 



Acknowledgments 7 



Definitions 7 



The Composition of the Plankton 10 



Comparison of Fresh-water and Marine Plankton 12 



Organisms of the Plankton 13 



Constituent Groups of the Annual Plankton of the Illinois River (Table) 16 

 Discussion of the Statistical Data of the Species composing the Plankton 



of the Illinois River in 1894-1899 18-290 



Cryptogamia ; 18-62 



Bacteriaceae 18 



Schizophyceae 19 



Discussion of Species 20 



Chlorophyceae 22 



Discussion of Species 24 



Bacillariaceae 34 



Factors controlling Diatom Production 35-43 



Diagram showing the seasonal distribution of diatoms, total 

 plankton, nitrates, and thermograph and hydrograph of Illi- 

 nois River at Havana for 1898 37 



Discussion of Species 43 



Conjugatae 59 



Discussion of Species 60 



Phanerogamia . 62 



Protozoa 62 



Mastigophora 63 



Location and Amplitude of Pulses of Chlorophyll-bearing Organ- 

 isms in the Illinois River (Table) 64 



Discussion of Species 68 



Rhizopoda 92 



Discussion of Species 95 



Heliozoa 113 



Discussion of Species 113 



Sporozoa 114 



Ciliata 115 



Discussion of Species 118 



Suctoria 131 



Discussion of Species 131 



Porifera.. 132 



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