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tity of water dipped from any part of the pond during this period always 
contained them. They could be seen feeding at any time on vegetable 
debris, Typha stems and alge. 
During the spring of 1909 the number began to decrease, and in the 
autumn they disappeared. They were never observed in 1910, although 
the pond was examined for them many times. This fact has an important 
bearing upon the general problem of distribution, as will be pointed out 
later. 
Cypris virens Jurine. 
This form has been present at all times but never developed in great 
quantity. Its greenish color and the fact that it is more closely confined 
to the substratum than Cypridopsis vidwa, render it less conspicuous. 
Cyclops serrulatus Fischer. 
Taken March 17, 1910, with eggs. Numerous in the shallower parts 
ot the pond during the latter part of the month. 
Cyclops bicuspidatus Claus. 
The typical form was present during the spring of 1910 but did not 
occur in great numbers. 
Most females taken were carrying egg sacks. During July and August 
as noted in the discussion of the plankton, this species occurred in great 
numbers, the maximum being on August 12, when 704,600 per 100 liters 
were present. However, the individuals were smaller and the stylets 
shorter and relatively thicker than in the spring forms. 
Pearse (05) reports this species as occurring in the spring in Ne- 
braska. In the Illinois River, it is reported as a winter form, Kofoid (’03). 
In Lake Michigan it is a summer form, Forbes (’82). In Wisconsin lakes 
it is active in the cooler parts of the year and passes the summer in a 
gelatinous cocoon. The seasonal distribution in different habitats of this 
variable form offers an enticing problem. 
Cyclops phaleratus Koch. 
Taken during March, 1910. Numerous April 15, 1911. Found among 
Typha and near the edge of the pond. 
TARDIGRADA. 
Macrobiotus. 
A form which was referred to this genus was taken in the spring of 
1910. They occurred in quantity on April 28, and for about one month 
