Cyclops. 
457 
Cyclops leuckarti Sars., Cyclops pulchellus Koch., and Cyclops 
brevispinosus Herrick. 
The three species of Cyclops named above stood second in num¬ 
ber among the pelagic Crustacea of July, averaging 30.5 per 
cent, for the entire month and increasing from 13 per cent, in 
Period I to 40.5 per cent, in Period II. They were counted to¬ 
gether, as no considerable difference in their vertical distribu¬ 
tion appeared, and as it was difficult or impossible to distin¬ 
guish the species from each other under a low power of the 
microscope. Observations made later in the year seem to show 
that Cyclops leuckarti was more abundant at greater depths than 
was Cyclops brevispinosus , but no sufficient number of observa¬ 
tions have been made to warrant a positive opinion. In all cases 
Cyclops brevispinosus was the most abundant, and ordinarily 
there were several times as many of that species as of the others. 
Number of Cyclops. —The average number of Cyclops caught in 
each series of hauls for the entire month was 2010. The area of the 
dredge was fa square meter, and its co-efficient probably about 
four, indicating a number of Cyclops of 200,000 per square meter 
of surface. The greatest number obtained was 5460 (J. 27; 6 
a. m.). The smallest number was 176 (J. 10; 8 p. m.). The 
variations in successive hauls were somewhat smaller than was the 
case in Diaptomus. The greatest variations observed in succes¬ 
sive catches were: 
July 27, 3 A. M... 2945 
July 27, 6 A. M. .. 5460 
July 27, 9 A. M. 3036 
This exceptionally large catch of Cyclops coincided with a 
similar large number of Diaptomus , and the number found was 
unusually large at all of the 4 upper levels (0-12 m.). The least 
variation in number was obtained in 4 consecutive catches on 
July 18, from noon to 9 p. m., the numbers being 1384, 1395, 
1381, and 1397, respectively. It may, however, be added that 
in these 4 catches the distribution in the different levels was 
quite different. The number caught in the 0-3 m level ranged 
from 498 to 906; in the 3-6 m. level, from 222 to 540; in the 
6-9 m. level, from 140 to 336. Thus while the total number of 
