527 



where in Spoon River tables have little significance save as 

 they express relative quantities in catches of chronological 

 sequence. Thus, in this table differences in successive months 

 have more significance than those in the same month of differ- 

 ent years. 



COMPARISON OF MONTHLY MEANS OF PLANKTON PRODUCTION IN ILLINOIS AND 

 SPOON RIVERS, BASED ON COINCIDENT CATCHES.* 





January 



February 



March 



April 



May 



June 



Year 



pi 



a 

 







p- 



Ph' 



pi 



a 

 

 



Cu 

 C/5 



X 



pi 



a 

 

 

 a 



C/3 



pi 



c 

 

 

 a. 



C/3 



pi 



pi 



a 

 

 

 a. 



00 



« 



Pi 



B 

 O 

 O 



Oh 



C/3 



1896 



1897 

 1898 

 1899 





























0.040 

 0. 100 

 O.IIO 



O.047 

 0.0l6 

 O.OOI 



0.380 

 0.430 

 0.540 



O.OO7 



0. 124 

 0.026 



5. 110 



O.O48 



5.620 

 10.310 



0.440 

 0.023 



0.270 

 5.280 



0.250 

 O.O96 



0.470 



OOI7 



0.220O.005 



















Monthly av. 



o.345]o.on 



0.083 



0.021 



0.450 



0.052 



5. no 



O.O48 



7.965 



0.232 



2.775 



O.I73 





July 



August 



September 



October 



November 



December 



Year 



r£ 



c 

 

 

 a 

 00 



rS 



c 



G 

 O 



a 

 00 



Pi 



a 

 

 

 a 



C/2 



P-i 



a 

 

 



Oh 

 CA1 



ei 



c 





 



Ph 

 CO 



Pi 



pi 



c 

 

 



Ph 



co 



1896 

 1897 

 1898 

 1899 







0.68 

 2.02 

 1.620 



0.004 

 0.056 

 0.002 



0.380 



n .920 



0.610 



O.005 

 5-130 

 0.002 



1. 105 



0.005 



0.020 1 0.005 

 0.665' 1. 671 

 0. 1400.001 



0.765 

 0.030 

 1 .260 



002 







0.599 



O.OOI 



O. I40 



0.036 



. 1 70 



O.OOI 



























Monthlyav. 



0. 140 



0.036 



1 

 1 .440 0.021 



4-30.3 



I .712 



0.638 



0.003 



0.2750.559 



0.685 



0.201 



*Amounts in this table are cubic centimeters of plankton per cubic meter of 

 water after subtracting from the total catch the estimated amount of silt. 



A detailed comparison of the production of the two streams 

 by months has been made elsewhere (see pp. 340-350). For 

 the purposes of the present discussion it will suffice to call 

 attention to a few salient features found in the somewhat 

 irregular data of the table. 



In but few averages does the plankton in Spoon River 

 equal in amount that of the Illinois. Not only is this true 

 of the monthly averages with but three exceptions, but 



