294 



amount not surpassed for this month in any subsequent year. 

 It may also be correlated with the continuance of stable con- 

 ditions. The nearest approach to this amount is found in 1897 

 (9.45 cm.^ Table III.), likewise in stable conditions. It is not im- 

 possible that there is more than one culmination in the months 

 of June and July, collections being at too great intervals to 

 suggest the direction of the movement in production. 



The flood of September attends a decline of the plankton 

 to a minimum of .34 on the 17th in the fluctuations in level on 

 the crest of the flood (PI. VIII.). Similar direction of movement 

 in production may be traced in 1895, 1896, and 1898. This 

 decline in production attends the beginning of the autumnal de- 

 cline in temperature, 10°-15° of which occur within this month. 



The hydrographic conditions during the remainder of the 

 year are exceedingly stable, there being a gradual rise of only 

 .5 ft. from the middle of October until the middle of December. 

 Beyond the insignificant rise in the October catch no movement 

 in production is evident. A comparison of these scanty data 

 with the curves of production in these months in 1895 and 1897, 

 both with low-water autumns, makes it evident that collections 

 in 1894 were too infrequent to serve as a basis for any conclu- 

 sions as to the average autumnal production in this year, and 

 raises the query as to whether considerable fluctuations of 

 pulse-like character might not have run their course in the in- 

 tervals between our collections. The higher averages in Octo- 

 ber-December in other years supports this suggestion. It is 

 evident that the monthly interval of plankton collection is too 

 infrequent to afford usable or significant data. 



The average of the ten collections in 1894 is 2.49 cm.\ and 

 that of the seven monthly averages 2.53 cm."' This is larger than 

 the averages for a similar period in 1896 and 1898 (.99 and 1.09 

 respectively) , both years of disturbed autumnal hydrograph. It 

 is much less than that of the last seven months of 1895 (7.15). 

 If, however, the exceptionally large collections of June-July 

 be omitted in this year, its average (of monthly means) falls 

 to 2.05. In the main, the hydrographic conditions in 1894 and 



