467 



nections with and contributions from the remaining backwaters. 

 The complications arising from the combination of these vari- 

 ous factors in varying degrees and the seasonal shifting of the 

 two periods in the several years, render any sweeping general- 

 izations impossible. 



The following table gives in parallel columns the monthly 

 means of plankton per m.^ and of river stages in feet above low- 

 water mark. 



PLANKTON PRODUCTION AND RIVER LEVELS. 



An inspection of the table shows at once the complexity of 

 the problem, and yields the following generalizations. 



In January-February, a period of sustained minimum tem- 

 peratures, high levels are attended by a small, and low levels 

 by a larger, plankton content, with the exception of stagnation 

 conditions in February, 1895. This contrast results from the 



