228 



BOSMINA AND HYDROGRAPHIC FLUCTUATIONS.* 



* + = 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 



