Cyclops. 
329 ' 
May 2d to 9th in 1896. The entire month may be included in 
the maximum in 1895, as all the catches made between May 3d 
and June 6th, 26 in number, were between 636,000 and 1,234,000 
per sq. m. In 1896 the limits of the maximum period may be 
set at April 14th and May 20th, during which time the numbers 
ranged from 763,000 to 2,359,000 per sq. m. The observations 
were 20 in number. The maximum catch recorded was nearly one- 
third larger than any other, although there were 7 catches 
made, ranging from 1,300,000 to 1,700,000 per sq. m. 
From these figures and from the averages, it is plain that the 
numbers were far greater in 1896 than in the former year. I 
attribute the difference to the earlier start which the species 
had in 1896. In that year reproduction began under the ice so 
that the numbers at the opening of the season were three or 
more times as great as in 1895. While the lake warmed some¬ 
what more rapidly in 1896, the difference was chiefly marked by 
the higher temperature of the lower water, which would aid the 
development of the species during the first part of April. 
The decline of Cyclops is seen from Table XI and diagram 15, to 
be as steady and rapid as its rise. In 1896 the numbers in the 
first half of June were smaller than in the latter part of March. 
In less than two weeks after the maximum the number had fallen 
to less than one-sixth of the maximum and a week later it was 
less than one-half of the smaller sum. 
This decline is doubtless due to the scarcity of food, to the 
increasing temperature of the water and, to increasing competi¬ 
tion. At no time during the spring rise are as many as five per 
cent, of the species provided with egg-sacs and almost none of 
the animals in the lower strata of the water become sexually 
mature. This fact indicates that the lake becomes so crowded 
with the early swarms of the species that the food is insufficient 
to allow their development to maturity. Not only so, but those 
individuals which are compelled to migrate into the deeper 
water find there little food and must perish in a short time. 
At the height of the Cyclops period there is very little alga 
visible in the catch. 
The influence of temperature is shown by the fact that the 
maximum is reached when the temperature of the lake is about 
