577 
profoundly the plankton production in this lake and in Quiver 
also. Although the average height for this year (6.975 ft.) is 
almost the same as in 1897 (6.903 ft.), the distribution of high 
water is such that the impounding function is exercised not 
only during the winter months, when production is low, but, 
owing to the recurrent floods, it is in operation to an unusual 
extent during the period from June to October, when produc- 
tion is wont, as a rule, to run low in these waters. Thus levels 
(Pl. XX XI.) are above 6 ft. fully half of this timeand are at all 
times above 4 ft. with the exception of 10 days in July. Not only 
does this increase the impounding function of these waters, but it 
decreases the relative occupation by vegetation in addition 
to reducing its actual extent by uprooting and removal. It 
also decreases the proportion which creek and spring waters 
form of the total content of the area, or impounds them long 
enough for the plankton to breed therein. 
The distribution of high water is such in this year that it 
affords an opportunity for increased production in the lake. 
In comparison with 1895, when production averaged 3.25 cm.‘ 
per m.* from April to the end of the year, we have 5.01 in 1896 
for the year asa whole. The average height of the river in 
1895 was 3.61 ft. (p. 163), in 1896, 6.98—an increase of 3.37 ft., 
or the equivalent of almost doubling the volume of water in 
the lake. So not only is the amount per cubic meter greatly 
increased, but the total run-off of plankton into the channel is 
multiplied by some undetermined factor. 
The net result of the hydrographic conditions of 1596 in 
Dogtish Lake is therefore an increase in its impounding func- 
tion at a time of large production (5.01),and its discharge 
- tends to raise the plankton content alike of Quiver Lake (2.59) 
and the river (1.16), but data are lacking which might enable 
us to compute its quantitative effect upon the plankton con- 
tent of either. 
Not only is the average production of Dogfish Lake greater 
than that of Quiver, but individual collections here exceed coin- 
cident ones there with the exceptions only of those on May 21 
