377 



profoundly the plankton production in this lake and in Quiver 

 also. Although the average height for this year (6.976 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 XXXI.) are above 6 ft. fully half of this time and 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 as a 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 1896 in 

 Dogfish 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 



