378 
and 22 and Aug. 15, when phenomenal declines appeared in 
Dogtish lake. In a similar way its production exceeds that in 
the river in every case but one, that of May 21. Thus produc- 
tion is prevalently higher here than in Quiver Lake and the 
river, to which it contributes its run-off, as a result of the im- 
pounding factor and, in this year, of the relative absence of veg- 
etation also. The impounding permits the growth of the plank- 
ton to utilize the nutriment derived from decay of vegetation 
and other sources before it is carried out of the lake. 
1897. 
(Table VI., Pl. XXXII.) 
There are but 6 collections here in 1897, in the first six 
months of the year, at approximately a monthly interval. The 
average production for this period is 2.23 cm.’ per m.*, with a 
maximum of 8.18 on Apr. 27. Since the collections are coin- 
cident in the river, Quiver Lake, and this lake, a comparison 
of production is facilitated. The similarity noted in the previ- 
ous year may be traced here also, and the relationship of the 
three areas remains in the main unchanged during this half of 
1897. Briefly, there is low production in all three under the 
ice in midwinter, with a slight increase in all in March, a ver- 
nal pulse in April followed by a decline in production in May 
in the lakes but not in the river, while in June the flood reduces 
the plankton content in the river but changes that in the lakes 
but little. The collections throughout the period show greater 
production in the lakes (Dogfish, 2.23, Quiver, 2.77) than in the 
river (average, 1.91) with the exception of the May collection 
(Dogfish, 1.94, Quiver, 1.29, river, 5.62). This drop in plankton 
content in the lakes below that of the stream occurs at the 
time of greatest increase in vegetation and rapid drop in levels, 
which increases the relative occupation by vegetation-—a factor 
from which the river is relatively free. The flood of June, 
flushing the stream, obscures the relationships of production at 
that season. In all collections but those of May and Feb. 26 
Dogfish Lake contains a more abundant plankton that Quiver 
