a7 
in amount certainly much in excess of the production at that 
time in Quiver Lake (.63) or the river (1.74). This large pro- 
duction in this locality is then, it seems, to be attributed to im- 
pounding and decaying vegetation combined with accession of 
adventitious planktonts. 
The average monthly production (3.3) in this lake is on the 
whole less than half that in the river (6.65) for the same period, 
and it exceeds by over fourfold that in Quiver Lake (.74), through 
which all its run-off passes to reach the river. Since the com- 
parison of the two lakes is based on coincident collections, these 
amounts may serve as a quantitative statement of the effect of 
the environmental differences. As vegetation is much the same 
in both lakes the difference in production must be attributed to 
some other factor presenting a difference which may be corre- 
lated with that in production. Such a factor is found in the 
impounding action, which is at a maximum in Dogfish Lake 
and is relatively much less in Quiver Lake at the point of our 
collections, where creek and spring water of recent origin cause 
a more rapid displacement of the contents of the lake and car- 
ry away the products of decay of vegetation before the plank- 
ton can reach the degree of development that it does in the 
more stable waters of Dogfish Lake. 
The run-off from this lake in this year would thus tend to 
enrich Quiver Lake, though not on an average of sufficient pro- 
duction toenrich the river even if it could reach it without 
mingling with that of Quiver Lake. However, owing to the fact 
that this lake receives no tributary creek or spring water, and 
except at high levels has no bottom-land current through it, we 
must infer that its run-off is confined—excepting only at stages 
of general overflow—almost wholly to stages of falling water. 
During rising levels and in fairly stable conditions its contribu- 
tions to Quiver Lake, and thus to the river, are practically n/. 
1896. 
(Table VI., Pl. XXXI.) 
There are 30 collections in this year, with a distribution 
