125 



DifiptoiiiKn.—As uotcfl above, two species were present, but they were 

 not counted separately. For the most part, Diaptonuis remained in the 

 upper ten meters of the lake as those found below this depth constituted 

 less than 5 per cent, of the total number of individuals taken in either a 

 day or a night series. They were found at the surface in sixteen of the 

 twenty day series, but, with two exceptions, there was a marked increase 

 in the number of individuals at the surface at night. This increase varied 

 from five to twenty-five fold. The two exceptions were surface catches 

 made on cloudy days. These differed l»ut little from the night surface 

 catches. The increase at the surface usually began about sunset and the 

 gi'eatest decrease occiu'red half an hour to an hour before sunrise. 



Fig. 1 shows the surface conditions for Diaptomus in the two all-night 

 series. The vertical spaces represent the numlter of individuals per hun- 

 dred liters of surface water and the horizontal spaces represent the time 

 between p. m. and G a. m. The curves show a striking similarity of 

 conditions although the observations were separated by a time interval 

 of three weeks. They show that the maximum number was found at 

 the surface at 7:30 p. m. on both occasions. Both also show a decided 

 decrease during the next linlf lunir. a second l>ut smaller rise at midnight, 

 a third near morning, and a fourth is indicated for the period immediately 

 following sunrise. Diaptomus was not found in the surface catch on 

 August 5 at 11 a. m. and there were IGU i>er 100 liters on August 27 at 

 9 a. ni. 



C i/clops.—fiexeval species were present but no attempt was made to 

 count them separately. They were distribiited through the entire depth 

 of the lake. Thej' were found at the surface in all the day catches. In 

 general, the night increase was comparatively small as it did not exceed 

 five fold. There Avas little or no difference between the surface catches 

 made on cloudy days and tliose made at night. 



The curves of Fig. 2 represent the status of Cyclops in the two all- 

 night series. The early evening conditions differ a great deal as there is 

 no maximum in the curve for August 27-28 corresponding to the 7:30 p. m. 

 maximum of August 5-0. Beyond this, however, the curves are very 

 similar. The surface catch on August 5 at 11 a. m. showed a total of 160 

 Cyclops per 1(X» liters and there were 200 on August 27, at 9 a. m. 



NaiipUi.— They were found throughout the entire depth of the lake 

 and showed no evidence of a movement. 



