XVll 



PAGE 



Affected by environmental factors 51° 



Approximation in time of pulses at different stations 510 



Normal regimen in our waters one of recurrent pulses of varying am- 

 plitudes 511 



Source and maintenance of potamoplankton S^l 



Problem stated 5^1 



Relation of seepage waters 5^2 



Relation of tributary streams 5^3 



Examination of Quiver Creek SU 



Collections and method 5^5 



Constituents of Quiver Creek plankton 5^6 



Comparison with plankton of river 5^7 



Quiver Creek a diluent of channel plankton S^^ 



Relative numbers of species in tributaries and river 519 



Chemical conditions S^o 



Examination of Spoon River • • • S^i 



Comparison of chemical conditions in Spoon and Illinois rivers. . . 521 



Resources of Spoon River adequate for large plankton 522 



Lack of time for breeding a cause of barrenness 523 



Comparison of quantitative plankton production in Spoon and 



Illinois rivers 5^3 



Errors resulting from leakage and silt • 5^3 



Statistics of production by monthly averages of all collections. . 525 



Ratio of production S^o 



Comparison of statistics of coincident catches 527 



Cause of periods of relatively larger production in Spoon River. 528 



Quantitative effect of access of tributary water formulated 529 



Qualitative analysis of plankton of Spoon and Illinois rivers 530 



Contrast in total population 53^ 



Relative development of different groups 53^ 



AlgEe 531 



Diatoms 532 



Rhizopoda 533 



Mastigophora 533 



Water-bloom of Spoon River ■ 533 



Infusoria 534 



Rotatoria • 534 



Entomostraca 53° 



Insect larvae 53 



Comparison of total number of species 537 



Comparison of seasonal routine 537 



Contrasts in autumnal plankton 53° 



Applicability of conclusions to other streams 539 



Effect of tributaries upon channel plankton 539 



Relation of backwaters to channel plankton 540 



Complexity of the problem 54° 



Impounding action of flood-plain 54^ 



Amount of impounded water 54i 



Duration of impounding 542 



