431 
hydrographic conditions. It is noticeable that production in 
the river is on the average 7- fold greater in July-August 
(Pl. VIIL.), during stable low water, when current is slackened 
and impounding most prolonged, than in June and September, 
when high levels and flushing by floods occur. 
The low level of production in the river in October-Decem- 
ber is exceptional. Similar hydrographic conditions in 1597 
Pl. XI.) yield a 5- to 10- fold greater production. It is not im- 
probable that the monthly collections of 1894 may be interca- 
lated in the depressions between plankton pulses of greater vol- 
ume, and thus inadequately represent the real production. Pro- 
duction in Quiver Lake in the months represented in our rec- 
ords in 1894 exceeded that in channel waters only in September- 
October, when a slight run-off occurred, and that in Thomp- 
son’s Lakein June, July, September, and December, but a run- 
off of any consequence occurred only in June and for a week 
each in July and September. Apparently the channel plank- 
ton in this year was largely independent and indigenous in 
origin, deriving but little enrichment from impounding back- 
waters, and not infrequently diluted by their contributions. 
1895. 
(Pl IX. XXVL, XXX. XXXII, XXXVI.) 
Tothe river, represented by 50 collections, Quiver Lake, 
by 13,and Thompson’s Lake, by 14, there are added this year, 
Dogfish Lake, represented by 12, and Flag Lake, by 4 collections 
in late autumn—a total of 93. The table on page 432 gives the 
monthly distribution of production in the several localities, 
and indicates their relation to the general averages. 
This is a year of lowest levels, averaging only 3.61 ft. above 
low water, and also one of high plankton content. On the basis 
of means of monthly averages, the average content in the river, 
5.91 em.’ per m.°, is the largest recorded, exceeding the average 
of all monthly averages, 2.71, by LIS per cent., and being sec- 
ond in the list if we base comparisons on the average of all col- 
lections. This high content in river waters must be attributed 
