323 
monia rose from a normal of less than 1 part per million in 
October to 5.6 on the 28th—the maximum record for all the 
analyses (Table X.). This is attended by slight increase in the 
oxygen consumed and the albuminoid ammonia as well as in 
the total organic nitrogen, all of which betoken the approach 
of stagnation. This is reflected in the fall of the plankton pro- 
duction to .03 em.* per m.* on the 28th. The extermination of 
the plankton did not approach that of Feb. 23, 1895, though 
there was a marked decrease in the number of planktonts ex- 
cepting only in stagnation ciliates. Temperatures during this 
month were at the winter minimum of approximately 32°, with 
only a slight increase to 36° with the rise of the second week. 
The plankton of this December in average production (.56 
~ em.') falls below that of all other years with the exception of 
the inadequately represented 1894. This relative falling off 
results, it seems, from the near. approach of stagnation, due to 
sewage which the stable low water permitted under the ice- 
sheet. 
As a whole, 1897 was a year of heavy plankton production 
when measurements are stated in plankton per cubic meter 
(3.69 cm.* if all collections are averaged ; 3.27 cm*., mean of 
monthly averages). If, however, we consider the slackened 
current and reduced volume of the discharge of the stream, it 
is evident that the fota/ production may not be greatly, if at 
all, increased during the low-water period of high plankton 
content. The vernal production, judging from results in simi- 
lar conditions in 1898, was possibly very large. It is evident 
on comparison, that our isolated vernal catches do not ade- 
quately represent the vernal production, and, furthermore, that 
the vernal maximum may have exceeded that of the low- 
water period in plankton content. Fuller representation in 
this period would doubtless have raised the yearly average. 
The high water, rapid current, and large discharge at this period 
combine to make the production in these conditions relatively 
very great, as compared, for example, with that of 1896, when 
the impounding action of the reservoir backwaters was slight, 
