Distribution of Cyclops. 459 



The minimum percentage in the upper 9 m. was 67.6 per cent. 

 (J. 10, 8 p. m.) and the maximum 99.33 per cent. (A. 2, 3 a. m.). 

 The catch from the lowest le\el, that from 15 m. to 18m., 

 contained on an average two specimens of Cyclops, with a 

 maximum of 10, and a minimum of 0, which last result was 

 found in about a quarter of the observations. The next level, 

 12-15 m., contained on the average 28 Cyclops^ with a maxi- 

 mum of 79, and a minimum of 1. Diaptomus had in this level 

 a maximum of 13. The average percentage of this level was 

 about 1.4 per cent, of the entire number of Cyclops, The 

 9-12 m. level contained on an average 176 specimens, with a 

 maximum of 723 and a minimum of 1. The average percentage 

 in this level was 8.77 per cent. For the entire month, there- 

 fore, just about 90 per cent, of the Cyclops were found in the 

 upper 9 meters. This distribution of Cyclops was true for the 

 deeper parts of the lake, as was also found in the case of Diap- 

 tomus. In observations made on the 21st of July, the number 

 of Cyclops found between the depths of 15 and 22 m. ranged 

 from to 9, with an average of about 2. 



In the upper 9 meters of the lake the distribution was 

 much as for Diaptomus. In the 0-3 m. level the average number 

 was 683, with a maximum of 2340 (A. 4, 6 a. m. ) and a minimum 

 of 30 (J. 10, 8 p. m.). The average percentage of the total 

 catch found in the upper level was 43, with a maximum of 66 

 per cent. (J. 18, 6 p. m.) and a minimum of 17 per cent. (J. 

 10, 8 p. m.). In the 3-6 m. level the average number was 612, 

 with a maximum of 1944 (J. 28, 3 a. m.) and a minimum of 60 

 (J. 10, 8 p. m.). The average percentage was 30.44, with a 

 maximum of 59 per cent. (J. 28, 12 p. m.) and a minimum of 

 16 per cent. (J. 14, 8 p. m., 18, 6 p. m.). The average number 

 for the 6-9 m. level was 329 with a maximum of 1146 (A. 2, 

 6 a. m.) and a minimum of 29 (J. 10, 8 p. m.) The average 

 per centage was 16.35, the maximum was 46 per cent. (J. 9, 7 

 p. m.) and the minimum was 5 per cent. (J. 28, 12 p. m.). 



Diurnal distribution. — In general, Cyclops shows the same facts 

 of distribution by day and night as does Diaptomus, but the 

 differences in distribution are not quite as plainly marked as in 

 that genus. If we compare the results for the entire month, we 



