390 
and by the middle of September the water had practically dis- 
appeared within its boundaries. 
The 7 collections average 4.59 cm.’ per m.’—about double 
the average production in the adjacent river, and in Quiver, 
and Dogfish lakes on coincident dates. Individual collections 
also exhibit in every case a greater plankton content in the 
lake than in the river. This area in this season thus contrib- 
utes to the enrichment of the channel waters, which its run-off 
enters, and its contributions exceed those of the lakes on the 
eastern side of the river. This higher production in this local- 
ity is, I believe, a corollary of the greater impounding function 
of Flag Lake, resulting from its freedom from tributary waters 
of recent origin, from its somewhat sheltered location—which 
checks the downward movement through its area of the gener- 
al currents of overflow, and from the enrichment of its im- 
pounded waters during this period by the decay of the abun- 
dant vegetation of the previous season, which, for the reasons 
just mentioned, is not extensively carried away by flood wa- 
ters. 
The fact that production appears to be so much less in 1897 
(4.59 cm.’ per m.*) than in the corresponding months of 1896 
(11.21) may be due to several factors ; to the greater dilution 
in the greater volume of overflow (cf. Pl. XX XIII. and XXXIV.) 
in the winter and spring floods of the latter year, to the greater 
abundance in 1896 of decaying organic matter accumulated by 
the vegetation of two preceding low-water seasons, and, possi- 
bly, in a measure, to the infrequency of collections in 1897 and 
the probable omission of the maxima of pulses of production 
which would tend to raise the average. 
The similarity in the movement of production in this and 
other localities will appear at once on comparison of Pl. XXXIV. 
with Pl. XI, XXVIII, and XXXII. The coincidence in the 
direction of the changes is precise in all of the 7 instances in 
the case of the river, in all but one for Quiver Lake, and in all 
but two in the case of Dogfish Lake. This is a period of max- 
imum overflow, when the individuality of these several locali- 
