Daphnia Jiyalina. 
389 
The table shows that the summer history of this spe 
cies was very different in the three years of my study. In 
July and August of 1894 the numbers were exceedingly smal 1 
smaller than in any of the three winters during which I have 
studied the species. In 1895 the numbers were large and re¬ 
mained large throughout the summer, gradually declining in 
September and October, and falling off rapidly in the latter 
part of October to the winter minimum without showing any 
marked reproductive period in late autumn. In 1894 and 1896 
the numbers, which were small and nearly equal in the latter 
part of August, rose steadily through September and October 
to a maximum in the latter part of October, and then fell off 
rapidly to reach the winter minimum in December or January. 
In late October, 1896, there were present enormous broods of new 
hatched Daphnias, which raised the number for that period beyond 
the records of any other. In 1896 the spring maximum was 
followed by a minimum about the middle of June, in which the 
numbers were scarcely one-quarter of the maximum. From this 
minimum there was a rapid recovery, which lasted for about a 
month and was followed by another marked depression. In 1895 
the spring maximum continued into June, and the early summer 
minimum came about the first of July. Portions of this mini¬ 
mum are included for the averages of the latter part of June and 
the early part of July, so that the number at the minimum ap¬ 
pears greater in the tables and diagram than it actually was. 
As a matter of fact, there was very little difference in the num¬ 
ber present in 1895 and 1896. In 1895 the recovery of the 
species from the early minimum came on as in 1896, but there 
was no reaction from the increase, and the number remained 
substantially unchanged through the entire summer. 
No observations were made in the spring of 1894, but the proba¬ 
ble history of the species was similar to that in the other years. 
There was a spring maximum followed by a marked minimum 
from which there was no reaction. This failure of the species 
to develop a summer brood seems to have been due to the pres¬ 
ence of Lyngbya in the upper strata of the water. 
The largest catches of this species were 331,000 per sq. m., 
Oct. 17, 1894; 565,000 June 6, 1895, and 1,049,000 Oct. 26, 1896. 
