357 
year, as will be seen on a comparison of Plates X. and XXVII. 
With a few exceptions which will be noted in the subsequent 
discussion, the trend of the production is similar in the two bodies 
of water to a most striking degree month by month throughout 
the year. 
With rising temperatures in February-March, production 
in the lake attains the unusual level of 1.75-1.85 em.’ per m.*, 
an amount not equaled at this season in this lake in any other 
year, and exceeding by 88- and 26-fold the production in the 
adjacent flood-swept stream (see table between pp. 342 and 343). 
This greater production in the lake is due, it seems, to the fact 
that Quiver Lake collections in these months represent the im- 
pounded backwaters of the eastern bottom-lands forced through 
the lake by the configuration of the eastern bluff (Pl. IL). Slight 
current and time for breeding permit in them a production not 
possible in the silt-laden rapidly flowing channel waters with 
which at our plankton station (Pl. Il.) they are contiguous 
during prevalent levels. The larger production in this year 
may be attributed to the enrichment of the water by the great 
mass of organic debris accumulated on the now submerged bot- 
tom-lands during the two preceding years of low water. 
The vernal pulses in the two waters coincide in the posi- 
tion of their limits and maxima though not in amplitude at 
any time, as will be seen on comparing Tables III. and V. and 
Plates X.and XXVII. The vernal development in the lake pro- 
ceeds more rapidly, appears earlier, and attains a greater am- 
plitude than it does in the river. Thus, on April 10 and 17 there 
is present in Quiver Lake 3.29 and 16.52 em.* of plankton per 
m.* to 1.68 and 4.45 in the river. The rate of increase is 4.7 times 
as rapid in the lake, and attains on the 17th a volume 3.7 times 
as great as that inthe river. The maximum (16.76) is almost 
twice that in the river (9.39). The large development (16.32) on 
the 17th indicates that the true maximum probably occurred a 
few days earlier in the lake than in the river. A partial ex- 
planation of this phenomenon, and also of the earlier and more 
rapid rise in production, may be found in the somewhat higher 
