Cyclops. Cyclops was much more abundant in 193C than in 

 1929, At no time did the curve for I929 cross the curve for 1930. 

 The average number for the period May I6 to October l5 was 6 per liter 

 in 1929 and l5 per liter in 1930. Not only was there a marked 

 difference in abundance, but the times of abundance were different. 

 In 1929 there was only one period of abundance (early May), and from 

 late May until late September there was little change in abundance. 

 In 1930 Cyclops began to increase earlier than in 1929, probably as 

 a result of the higher water temperatures in 1930. There were two 

 periods of abundance in 1930, and both came later than the one of 1929* 

 There were also two periods of abundance in 1928, but the times of 

 appearance were quite different. In 1928 they came in late May and 

 early July rather than in late June and early August, as in 1930, 

 The average number for the eight periods between late May and early 

 October was 8 per liter, which is slightly more than that for 1929> and a 

 little more than one half that of 1930, 



Daphnia . Daphnia was equally abundant in 1929 and 1930, For 

 the period May 16 to October l5 the average number was h per liter. 

 It began to increase earlier in 1930 bvit at a slower rate, so that 

 the maximum was reached at the same time. Following this, the decline 

 was also slower in 1930, and the July minimum was reached somewhat 

 later. The second increase for 1930 was not early as marked as in 



1929 but its appearance in the same relative position suggests that 

 it was real and not the result of inacciirate counting or inadequate 

 sampling. The curves for the two years show remarkably close agree- 

 ment, both in numbers present and in the times of abundance. Two 

 periods of abundance were found in 1928 also, but they came at some- 

 what earlier dates. The average count was 5 per liter for the eight 

 periods represented in the time between late May and early October, 



Nauplii, The curves for the copepod nauplii in 1929 and 



1930 are widely different. It has been pointed out before that there 

 is some evidence that the nauplii were on the decline in late May of 

 1929, and it seems probable that if data were available, the curves 

 would agree closely for the early spring period. The marked differ- 

 ence in abundance in the two years for late May and June probably 

 resulted from the higher temperature of 1930. In 1930 the nauplii 

 declined rather consistently from the high point of June, while in 

 1929 they increased during June and July, declined in early August, 

 but increased again in late August, It seems probable that the 

 discrepancies in the two curves resulted from the. different start in 

 development during June. The average number present during the 

 period May I6 to October l5 was approximately the same in the two 



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