491 



PLANKTON PRODUCTION IN MATANZAS LAKE COMPARED WITH THAT IN 

 QUIVER AND DOGFISH LAKES. 



Date 



895 



897 



S July 9, 10 



} August 14, 15 



Uuiy 



I August 



Uuiy 



( August 



Uuiy 



} August 



Uuly 



I August 



Uuly 



( August 



Averages,^ l"'^"":' 

 ^ '(August. 



Matanzas Lake 



2.40 

 6.20 



Quiver Lake 



■30 

 3-42 



2.20 

 0.74 



0-37 

 o. 21 



0.30 

 2.46 



0.89 

 0.21 



o. 16 



0.22 



0.78 

 0.77 



Dogfish Lake 



1. 18 

 2.90 



0.91 

 391 



1.95 

 2.51 



of collection above indicated is approximately twice that of 

 Quiver and Dogfish lakes, where vegetation was at that time 

 somewhat more abundant. In 1896 Quiver Lake was freer from 

 vegetation than at any other time in the period of our opera- 

 tions, and the contrast l)etween the production of the two 

 lakes appears greater if we consider other years or the average 

 for all collections in the months named. On the latter basis 

 the ratio rises to 3 to 1 for July and 8 to 1 for August in the 

 comparison of Matanzas and Quiver lakes. In the case of Dog- 

 fish Lake the contrast is less striking, but still evident. Ma- 

 tanzas Lake, similar in its environment to Quiver Lake save in 

 the matter of vegetation, thus produces a more abundant plank- 

 ton, and we may infer that the vegetation of the latter is in- 

 imical to the development of plankton in its waters. 



A second line of evidence bearing upon the question under 

 discussion is to be found in the production in Quiver Lake itself 

 under different conditions of vegetation. In 1894, and still 

 more in 1895, owing to low water in early summer, vegetation 

 was very abundant in Quiver Lake. The growth of Cerato- 

 phyllum and Elodea choked its waters from shore to shore and 

 from bottom to surface except in a narrow poorly defined chan- 



