125 



l)iaiitiiiiiii>>.—\>i. iiotefl ;il)ove, two species were present, but they were 

 not counted separately. For the most part. Diaptonius remained in the 

 upper ten meters of the hil^e as those found below this depth constituted 

 less than 5 per cent, of tlie 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 twi'uty-five fold. The two exceptions were surface catches 

 made on cloudy days. These differed but little from the night surface 

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

 greatest decrease occurred half an hour to an hour before sunrise. 



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

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

 dred liters of surface water and the horizontal spaces rei)resent the time 

 between (» p. m. and (J a. m. The curves show a striking sinularity of 

 conditions although the observations were separated by a time interval 

 of three weeks. They show tliat the maxinuun number was found at 

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

 decrease during the next half hour, a second but smaller rise at midnight, 

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

 following sunrise. l>iai)tomus Avas not foimd in the surface catch on 

 August .J at 11 a. m. and there were 100 per 100 liters on August 2.7 at 

 9 a. m. 



('//r?o/>.*(.— Several species were present but no attempt was made to 

 count them separately. They were distributed through the entire depth 

 of the lake. They wen- 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 those made at night. 



The curves of Fig. 2 rei)resent 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:^0 p. m. 

 maximum of August o-O. Beyond this, however, the curves are very 

 similar. The surface catch on August o at 11 a. m. showed a total of 100 

 Cyclops per KXi liters and there were 2(X> on August 27. at a. m. 



Nau pi a. —They were found throughout the entire depth of the lake 

 and showed no evidence of a movement. 



