444 
September. Quiver Lake, however (Pl. XXVIII.), pursues a 
different course, production there dropping to a level rarely 
exceeding .5 cm.’ for the remainder of the year. This results 
from the greater ve/ative volume of spring and creek water in 
this lake. The discharge from Quiver Creek and the marginal 
springs continued with relatively much less diminution through 
the autumnal drouth than that from Spoon River, with the 
result of making this lake far less productive of plankton at 
this season than Spoon River (cf. Pl. XXIII. and XXVIII.). 
1898. 
(Pl. XIL, XXIV., XXIX., XXXIV., XXXIX., XLIL.) 
This year is represented by 52 collections in the Illinois 
and 11 in Spoon River, and by 26, 6, 25, and 22 respectively in 
Quiver, Flag, Thompson’s, and Phelps lakes. It was a year of 
normally located and fully developed spring floods, followed 
by low water in summer much disturbed by minor floods, with 
a subsequent autumnal rise of unusual proportions. This re- 
sulted in the highest average river levels in our years of opera- 
tion, 8.02 ft.—a level almost equaling bank height. 
The accompanying table gives the data of comparative 
production of the different localities in this year. 
PLANKTON PRODUCTION IN 1808.* 
Station Jan. Feb. | March | April | May | June July 
Ill. River...|-++| .45 |+| .27 [+] .33 |—] 4.40 cae 30 —| 3.96 |—| .58 
Spoon River | + .O17;—| .O16]-+] .124]..}..... 023} —| .096|-| .036 
QuiverLake|—| .o2 |—| .31 }—] .74 j|—| .53 +116. 27 |+| 2.23 |—| .16 
Bilaip Traikes ilar llssrecss seat [ae ae eve | ae | Ee een Er alevever seed lave tetere cteieta| eet eieuetetiers —| .36 
Thomp. L.. +1 7:22 |—| .64 |—|. —| 2. 44 ne 94 |—|10.13 | —| 2.08 
BhelpsGakellis|eenelleeleeeeee | —- —| 5. 60 | +'40.44 |-+]27.67 | —| 6.97 
Mean of 
Station Aug] Se sept: Oct. Nov. | Dec. monthly 
averages 
Illinois River....... — 39 |= |PR69 SS 2a SS ese Eom tetos 
Spoon River........ | — .002}—] .002}—| .oo1|—] .oo1|—} .oo1}—| .02 
Quiver Lake....... — -22 |}—} .33 |—| .23 |}+] .73 ; +) 1.74 |+] 1.969 
Flag Lake......... = .03 |+115.54 |..|.....- = eo 5050 lel eae —| 5.31 
Thompson’s Lake.. | —| 2.63 |—| 2.66 |—| 1.25 |—| 1.17 |+] 3.58 | —| 5.06 
Phelps Lake....... +1139.85 | 147-25 | +/32.31 |-+[5t.14 | +)21.96 |+137.34 
* The minus s sign signifies below average and the plus sign above. 
