44] 
drying up of the Jake. In September the lake did temporarily 
dry up only to be re-entered by the October flood, in which an 
unusual plankton (51.6 em.*) at once developed. 
1897. 
(Pl. XL, XXIIL, XXVIIL., XXXII, XXXIV., XXXVIII., XLI. ) 
This year is represented by 34 collections in the Illinois, 
and 13 in Spoon River, and by 24, 6, 7, 18, and 9, in Quiver, 
Dogtish, Flag, Thompson’s, and Phelps lakes. It was a year of 
protracted winter and spring flood, a late June rise, and pro- 
longed low water in summer and autumn. The data of compar- 
ative production are given in the accompanying table. 
PLANKTON PRODUCTION IN 1897.* 
Station | Feb. | March | April May June July 
Illinois River........ —| .o4 [+] .38 |+) 5.11 |—| 5.62 |—| .27 |+) 4.69 
SPOOnMRIVET «2 sae +) .047] — ‘B07 | -048|-+] .440;-++] .250)..]...... 
Quiver Lake.......... —| -I9 |—| 34 +)13.38 3 1.29 |+/ 1.26 |+] .89 
Dogfish Lake ....... = 15 [—| .48 | —| 8.18 |—| 1.94 Fil Pe he Reed ee ae 
Hlapewiakessenes osc —| .07 |—| .83 ;—| 8.55 | —|10.61 +) 4-87 [+] 7.13 
Thompson's Lake... |—, .27 |—| .65 |= 10.38 ;}—| 7.88 ;—] 3.59 |}—| 3-31 
Phelps: Eake™...mi- « —  .19 le 1.44 |—| 4.26 | 22:58 |-| 2 1+] 9.49 
Mean of 
Station Aug. | Sept. Oct. Nov. Dec. monthly 
i averages 
Illinois River........ —| 3.65 |+! 8.83 [+] 5.95 |+) 1.00 |—. .56 |+} 3.28 
Spoon RVers. 6. <<) + SETA SE oe 2 Wl lel lesen \e 1.671 | +. -559|+| 1.22 
Quiver Lake-<<.../-..- —| .2r |-| .16 ;}—| .04 |—| .09 |) — 007| —| 1.71 
1 Oey rl vil Dev eee ae | | el ape IG | De | FF ee line eae: —| 2.65 
IMES ILE) RS cob an cote snes So dello sopced Ma aasooe ia ae === == —| 5-34 
Thompson’s Lake ... +)19.40 +)1o.0o1 | +/35.35 | +]16.67 =F 6.98 |+}10.41 
Phelps Lake.......+5 —|25.70 | Bornes Be ieee, | allen #8 | oefeeeees —| 9.15 
*The minus sign signifies below average and the plus sign above. 
The infrequency of collections in January-June and the 
suspension of work in Dogfish, Flag, and Phelps lakes before the 
year ended, render general comparisons with other years of less 
value because of insufficient data. 
The annual channel production, 3.28 em.’ per m.*,—the mean 
of monthly averages,—or 3.69, the average of all collections, is 
21 or 68 per cent, respectively above the means, and 6 of the 11 
