6 
525 
COMPARISON OF MONTHLY MEANS OF PLANKTON PRODUCTION IN ILLINOIS 
AND SPOON RIVERS, BASED ON ALL CATCHES.* 
January | February March April May June 
| 
Ss A ae a We apnea wee ee! [eT aa IY soe 
pa a | eles a | = S m gS 4 Ss 
= 2 = ° = ce) S 2) Be =) : 2) 
= ° = (e) = ° = o = fe} = ° 
= or || = | 4 a | = a, on a. = a 
Farag PL | a elpa@a Pinal n n 
itty) | ASE abeteal ouaee| lon toe liana ol oiiact! baooGel SGcesd laeAocl lbemn ON 7A eee 
PBQG 1 tls alied. ons OLOU eo S2105|| we ere| cies = Ot Nason Goaralao sre BOEAZ |. 5 sistels 
TOoGe |OFOnN| er O. Oz|encne OLO7 | ener RalyAeSeraec Hine) |Reore ON /25eeeea 
USOZs qilerstelers| leprae 0.04:0.047| 0.380.007} 5.11] 0.048 See al 0.27 | 0.250 
1898 0.45 |0.017 0.27)0.016 0.33/0.124] 4.40]...... II.30|0.023| 3.96 | 0.006 
1899 0-18 0.005 0.81,0.001 N2EIOVG26| Meee ee raee Mena Reemc ins eee lanes 
Monthly av.'o.213/0.011 0.23/0.021! 0.27:0.052! 4.59! 0.048! 6.08!0.232! 7.22 | 0.173 
July August |September| October | November | December 
cea Ree mira etl). oat purse leet]. <r Biiliccee| en 
m4 gz | = | oa | a I = =| ~ a 
iss ° — ° is ce) oa ro) = f°] = ° 
= ° = ° = le] = ° = 2) = 5°) 
= a} 4 yer = a | 4 a, m a = roe 
hs n Nn 79) n n n 
TOQAN Dp 5:22 |os13 <i GQzO7|e <6 Mas sooae ©. 61) ee 05 ONMOloeeere ONO pea 
nelolse | eae 11] Aiea G08 |r TG 2| x17. os CLY|ISnoniee 3202). <5. TWA ve costars 
1896) |U.44) |e. I.12/0.018| 0.38]0.005] 1.11] 0.005 | 0.02/0.005] 0.76 | 0.002 
Lieye Peep anes 3.65|0.652] 8.83/5.130] 5.95]...... 00|1.671| 0.56 | 0.599 
1898 0.58 |0.036| 0.91|0.002| 0.69/0.002| 0.24} 0.001 | 0.25\0.001) 0.99 | 0.001 
Metre Kea mallee ral dion |sgeed sadod| Series Bestc lanpoco| eto amo) emethod bltomics 
Monthly av.'4.23 10.036 3.810.224! 2.56l1.712 1.70 0.003! 0.8810.559 0.71 | 0.201 
*Amountsin this table are cubic centimeters of plankton per cubic meter of 
water after subtracting from the total catch the estimated amount of silt. 
meters. This is 4.7 times as much as the average of all the 
Spoon River collections—11.5 times, if we omit the two 
exceptional collections of September 11 and 30, 1897, and 44 
times, if we exclude the low-water period of the autumn of 
1897 from both averages. This latter ratio, 1 to 44, represents 
the relative plankton content of the two streams except during 
periods of prolonged and extreme low water. Even in such 
low-water periods the waters of the tributary are less pro- 
ductive than those of the main stream. For example, the aver- 
ages of the monthly averages of production for July—October, 
inclusive, in the two streams are respectively 2.89 and 5.78 em.* 
