476 
So also in 1897, the means of our records of water tempera- 
tures for September, October, and November of that year are 
2.9°, 7.6°, and 2.7° above the average of the monthly means for 
all years. This maintenance of high temperatures into the pe- 
riod of normal autumnal decline is apparently one of the fac- 
tors tending to make production in these months of this year 
greatly exceed that of the same season in other years. In chan- 
nel waters in these months of 1897 (see table following p. 342) 
production is from 13 to 250 per cent. above the mean of all 
years, and often 10- to 20-fold that in other years. In Thompson’s 
Lake the excess in 1897 is even greater, ranging from 87 to 233 
per cent. of the mean of all years, and from 1.6 to 28 times that 
in the same months in other years. The higher temperatures 
do not suffice, however, in the case of Quiver Lake, to overcome 
the other factors tending to depress production there in these 
months, and we must conclude that, although all-pervading 
and potent, temperature is nevertheless not always pre-emi- 
nent among the environing factors of the plankton. 
We thus find that in a general way, in conjunction -with 
other factors, rising temperatures tend to increase, and falling 
to decrease, plankton production, and that in the same locality 
the warmer months generally yield more plankton than the 
colder ones. On the other hand, minimum temperatures when 
once established are not of themselves inimical to a considera- 
ble plankton production. Evidence of this is to be found in 
the not infrequently increased production in December over 
that of several months preceding. This is perhaps most notice- 
able in the records of 1898. Thus in channel waters the am- 
plitude of the December pulse (PI. XII.) exceeds that of all 
other months since the last of June, and the December maxi- 
mum in Phelps Lake (48.14) exceeds in amplitude all other pro- 
duction in our records for 1898 in all other localities save only the 
single apex of the vernal pulse (51.39) in Thompson’s Lake. It 
is, however, only about one fifth of the August maximum 
(224.48, Pl. XLII.) in Phelps Lake itself, so that the depressing 
effect of lower temperatures is still apparent if we limit com- 
parisons to a single locality. 
