228 
BosMINA AND HyDROGRAPHIC FLUCTUATIONS.* 
July August September - 
cea Total B } Total Bosmina Total | Bosmina 
| movement, enigs eae movement, 3 movement, | Z 
in feet perm: in feet Per a in feet PEE am 
=359 OE = 2 
1897 5 (6), ils} 2.6 3,973 6 3 O22 
| +1.1 +0 + .4 
| —6.9 —3.3 —2.6 
1SOS Wea 140 sl 10 6 ; | 15 
+ .1 +4.4 +3.4 | 
October November December 
Year Total : Total : Total : 
Bosmina Bosmina Bosmina 
movement, movement, a movement, 3 
er m.3 erm erm 
in feet P ; in feet PB : in feet iP 
— .l — 7 — .6 
1897 6 55875 DP 1,680 22 1585 
= eer) +1.5 ae a 
—1.1 — .6 —2.8 
1898 | 3.9 780 32 32 Sy gts) 60 
| +2.8 +2.6 +1.0 
* + = rising levels; — = falling levels. 
173 Bosmina in 1898. It is also true that months in which the 
disparity in stability is greatest are those in which the Bosmina 
ratios are greatest, and vice versa. It seems very probable that 
the increased current, the lessened time for breeding, and the greater 
burden of silt in flood conditions, especially rising waters, do not 
conduce to the rapid increase of Bosmina in channel plankton. 
The effect of the high temperatures of the late autumn of 1897 
is apparent in the amplitude of the October, November, and De- 
cember pulses (20,400, 3,440, and 3,440, respectively), which exceed 
those of all other years at this season. Temperature thus plays— 
perhaps by virtue of its relation to the food supply—an important 
