27 
or 
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 
EA OE fe2 hl = ns =o ec ead Pl 
|) ey RW |) tee | § ei || ey) is fe) | I 
uns fo} at fo} — fo} —s ° — fo} aes fo} 
= fo} = ° _ | 2) _ ° = ° — 1) 
—! Qa i! Q Lad Q Et Q, a Q = Qa 
n | a a | a aoe n 
HSC ga ete rerec ell neces feces este | ex cenesell Ceseyrortos fosater air |lecsyeyoies tevevensyel|- ccvecolters| [tye taisrl| wevorers||fareicictes= 
soy |e ll Seo 0.040/0.047| 0.380!0.007|5.110|0.048) 5.620\0.440/0.270| 0.250 
1898 0.4700.017 0. 100]0 016 0.4300. 124 Sisistans||lz cece 10. 310|0 ,.023/5 .280) 0.096 
1899 _|0.220/0.005}0. 110}0.001| 0.540/0.026).....].....].-.---].----|---+-]-.---- 
Monthly av.|o. 345/0.011 0.08310.021 0.45010.052|5 .11010.048 7 .965|0.232|2.775] 0.173 
July August {September | October | November] December 
Yar ised | oe eam eee See |) A ies 2 
es I = z| ce g ca I ma g m4 I 
as fe) pal c an o) rm io} == (o) = 2} 
= ie) = ° = ° = 12) = ° _ io} 
a ay | o a ey |) =) a, 4 a) | a, 
n | | a an | |) ee || [eee 
1s)=  \Soonallaeoes 0.68 |o.004] 0.380]0.005|1.105|0.005] 0.020'0.005/0.765| 0.002 
ESOT llhaerstetal|ises eters 2/02 /OLOGO|NiN. 20/5 L30lyacrellle estos 0.665'1.671|0.030| 0.599 
1898 jo. 140]0.036|1.620'0.002] 0.610/0.002/0.170'0.001 0.140 0.001 1.260] 0.001 
LOOSEN ettecota Reeser Iie srotell rere aero enamel ccteellle okt eh amrerdl[Mewcclloe 5 e-o% 
Monthly av.'o. 140|0.036|1.440'0.021 4.303|1.712|0.638.0.003| 0.275 0.559,0.685 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 
