D. pulicaria. 471 



accuracy of the counting is to be made here as was made in re- 

 card to the 0-3 m. level. 



With the 6-9 m. level came a great increase in number. The 

 average for the whole period was 37 per observation. The max- 

 imum was 196, the minimum 0. In Period I the average num- 

 ber was 27; in Period II, 39; in Period III, 70, while in 

 Period IV an average of only 5 was obtained. During the 

 whole month D. pulicaria averaged nearly 4 per cent, of the 

 catch in this level, the percentage ranging from .4 per cent, in 

 Period IV to 6 per cent, in Period II. An average of 36 per 

 cent, of all the individuals of this species was obtained from 

 this level, the percentage ranging from 56 per cent, in Period 

 III to 27 per cent in Period I. 



An even larger number was obtained from the 9-12 m. level, 

 the average for the month being 42, with a maximum of 138 

 and a minimum of 0. The average numbers in the successive 

 periods were 33, 59, 48, and 13, respectively. Since the number 

 of Cyclops and of Diaptomus was very much smaller in this 

 level than in the upper levels of the lake, D. pulicaria consti- 

 tutes a considerable fraction of the catch made at this level. 

 The percentage is about 3 per cent, in Period IV, where the 

 average number of Diaptomus and Cyclops was largest on ac- 

 count of the disturbed condition of the water, and where an 

 average of only 13 specimens of D. pulicaria were caught. In 

 Period II, 25.5 per cent, of the total catch from this level con- 

 sisted of D. pulicaria. The tables show that in this period very 

 few specimens of Diaptomus and Cyclops were found at this 

 level, and also that the greatest absolute number of D. pulicaria 

 was found there. In Periods I and III the percentage was be- 

 tween 9 and 10. D. pulicaria constituted 11.5 per cent, of the 

 average catch from this level for the entire month. 



In the 12-15 m. level a considerable number of this species 

 was found, although the number declined very greatly from 

 the 9-12 m. level. Probably the greater portion of those cred- 

 ited to the 12-15 m. level were obtained from the upper part, 

 since almost no specimens were found below 15 m. The aver- 

 age number for the month was 16, with a maximum of 152 and 

 a minimum of 0. This maximum is more than twice as large as 



