556 Wisconsin Academy of Sciences, Arts f and Letters. 
vidual was found in the night catches above this region. On 
the contrary, the only individual found in Lake Geneva was 
taken in a surface catch at night. 
Diaptomvs. 
This genus was represented in each of the ten lakes. Diur¬ 
nal movement was. noted in seven, ranging in extent from a 
quarter of a meter to five meters. The time' of arrival of the 
adults at the surface in the evening varied between the ex¬ 
tremes of an hour before sunset and half an hour after sunset. 
In the morning, they left the surface as early as two hours be¬ 
fore sunrise in one case, while in another they remained as late 
as an hour and a, half after sunrise. 
Cyclops. 
Representatives of this genus were' found in all the lakes. 
Diurnal movement was observed in four, ranging in extent from 
one meter to eight meters. 
Morning and evening catches were made in two of the four 
lakes in which there was a movement of Cyclops. In one lake, 
adults came to the surface during the third half hour after sun¬ 
set and in the other they had not appeared as late as twP and a 
half hours after sunset. In one case 1 , they left the surface dur¬ 
ing the second half hour before sunrise and in the other about 
sunrise. 
Nauplii. 
Nauplii were present in all the lakes. They showed no diur¬ 
nal movement. 
Corethra larvae.- 
Corethra larvae were found in six lakes. There was a move¬ 
ment of them in five lakes ranging in extent from two to nine¬ 
teen meters. 
WHAT DIURNAL MOVEMENT IS. 
In a previous paper (8b, p. 128), the statement is made that 
diurnal movement does not mean that the various forms core 
gregate at the surface at night in swarms. This is shown by 
