228 
BosMINA AND HYDROGRAPHIC FLUCTUATIONS.* 























| July | August September 
Year| | 
| Total Bosmina | Total | Bosmina Total Bosmina 
| movement, 3 | movement, es movement, Beate 
in feet Pee: in feet aaa ts in feet in 
—3.9 —2.6 | — .2 | 
13975 6,213 4) 256 3973 6 |v aoe 
| +1.1 +0 | + .4 | 
= (9) —3.3 —2.6 
T3983 |) 7. 140 etl 10 6 15 
+ .1 +4.4 +3.4 
October | November December 
ae Total Bosmina Total Bosmina Total Bosmina 
movement, eae as movement, tne movement, i ne 
in feet Be ; in feet pea in feet Pp 
— .l — 7 — .6 
1897 6 5,875 Da) 1,680 il 1585 
+ .5 +1.5 =O 
—1.1 — .6 —2.8 
1898 | 3.9 780 See. 32 3.8 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 
a 

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