353 
exceptions of repeated vertical hauls (Table V.) in the winter 
flood of 1895-96—from the beginning till May 22, 1896. After 
this date all collections were made with the pump. 
This lake is a type of some other bottom-land waters, spring- 
fed and rich in vegetation, and our collections suffice to show 
the relation which these bear to production in the adjacent 
channel waters. They also serve for comparison of production 
with that in other backwaters less rich in vegetation, and since 
the quantity of vegetation in Quiver Lake varied from year to 
year they also throw some light on the effect of vegetation up- 
on plankton production in a single area. 
PLANKTON PRODUCTION, 
1894. 
(Table V., Pl. XXV.) 
The 14 collections in this year average 1.08 em.’ per m.* to 
2.49 cm.’ in the Illinois. The maximum (3.50) falls on Septem- 
ber 6. There isa striking resemblance in the planktograph of 
Quiver Lake for this year (Pl. XXV.) and that of the adjacent 
channel (PI. VIII). The amplitude is generally less in the form- 
er, but the direction of movement is the samein both. The 
June production (monthly average) is low in both Quiver Lake 
(.25) andthe Illinois (.74); it rises in July (2.20 and 5.12); and 
it declines in September (2.12 and 1.36) toa minimum of .80 and 
384, from which it recovers slightly in October (.95 and .61) to 
fall again in November (.02 and .10) and December (.03 and 
10). The only exception to this parallelism in the movement 
in production is seen in August, when in Quiver Lake produc- 
tion drops to .74 but attains a seasonal maximum of 9.67 in the 
river. Aside from the fact that this is the season of greatest 
predominance of vegetation in the lake, owing both to growth 
and to low river levels, there seems to be nothing in the en- 
vironmental conditions to be correlated with this contrast. 
While as a whole for this year the contributions of Quiver 
Lake (1.08 em.’ per m.*), as shown by our data, only result in 
