48 THE LIFE OF DEVILS LAKE 



show any influence of light on the distribution of the plancton 

 animals. In most of this work 500 c. c. samples were used, but in 

 two series 19 litres were pumped thru a Kofoid net, the amount 

 being measured with a water meter. The tests usually covered a 

 period of twenty-four hours in quiet weather, and were taken on a 

 line across Creel Bay. at both shores, and at the 0, 0.6, 0.9 and 

 3.0 m. depth near the middle of the bay. 



The collections were made at approximately the following 

 hours: 12 N. 5. and 9 p. m., 12 M., and 9 a. m. 



One reason for the failure of the tests to give definite results 

 is possibly the irregular distribution of the plancton, as Moberg 

 (I.e.) has already suggested. 



EAST LAKE (pi. 2) 



East Lake is a long, narrow body of water extending southeast 

 from the "Narrows" for some 17 km. It formerly was connected 

 with Main Lake on the one hand and with Lamoreau Lake on the 

 other, forming one continuous body of water, and is so represented 

 on the present maps. It was separated from Main and Lamoreau 

 Lakes about 1903. At the present time it has retreated about 2 

 km. from Lamoreau Lake, its former bed being occupied by a low, 

 grassy swale in which are two nearly fresh water ponds, evidently 

 spring fed. 



With its separation from the other parts of Devils Lake the 

 fall in East Lake has been rapid. When work -was begun in 1911 

 it had a maximum depth of about 3 m., while at present it can 

 hardly be more than a metre. The reasons for this are possibly 

 threefold. In the first place the shores of East Lake are in gen- 

 eral very low and flat and the drainage per unit of lake area is 

 probably much less than that of the other parts. In the second 

 place the supply from springs may be less, altho this source of 

 supply is probably very small in all three bodies. Thirdly the 

 shallow waters of East Lake are more disturbed by the wind than 

 are the deeper waters of the other two parts, and hence the evapora- 

 tion is greater. 



The decrease in depth has naturally been accompanied by pro- 

 found changes in its physics, chemistry and biology. I have but 

 two color records for East Lake, both of which were made on sam- 

 ples which had been collected several days previously. One of 

 these gave a reading of 86 for the surface and 64 for the bottom, 

 and the other of 68 for the surface and 40 for the bottom. 



The few turbidity readings taken show a range of from 25 to 

 46. 



Some curves of temperature and dissolved gases are given in 

 figures 10 and 11. They show differences between top and 



