548 Wisconsin Academy of Sciences, Arts, and Letters. 
bright, sunny days. During the first half of the month, adults 
were at a depth of three-fourths to one meter in the daytime. 
On the 5 th, they came to the surface during the: first half hour 
after sunset but, on the 8th, they were found in the surface 
catch made half an hour before sunset. On the 12th, they left 
the surface during the second half hour 1 before sunrise. In the 
day series of the 25th, adults were at a, depth of only a quar¬ 
ter of a meter and they had not yet appeared at the surface 
three and a quarter 1 hours after sunset. 
In 1901, diurnal movement was noted as early as April 24, 
only twelve days after the disappearance of the ice. At this 
time the water had a temperature of 7.2° C. at the surface and 
4.8° at the bottom, eighteen meters. April 24, 25, 29 and May 
3, young were rare and there was practically no difference be¬ 
tween day and night conditions. On these dates, adults were 
found at a depth of one meter in the day catches but they came 
to the surface at night. In the day catches of May 15, young 
were at a, depth of one meter and adults half a meter 1 deeper. 
Both appeared at the surface about sunset. The adults left 
the surface about an hour before sunrise and young were still 
present one hour after sunrise. On May 28, young were at 
the surface and adults at a depth of one meter in the daytime. 
The latter came to the surface at night. 
In June, young I), hyalina were found at a depth of half a 
meter in two day series. They were: found at. the surface: at 
the beginning of each of the three evening series and one of 
these was begun as early as three hours before sunset. In the 
meming catches they were at the surface as late as an hour and 
a half after sunrise. In the two day series:, adults were at a 
depth of one meter. In two 1 evening series, they came to the 
surface nearly an hour before sunset and not until the second 
half hour after sunset in the third series. In the 1 two morning 
series, adults left the surface during the first half hour after 
sunrise. 
Daphnia retrocurva .—This species was found in October and 
June but no diurnal movement was noted. It was found at a 
greater depth, however, in the daytime than Daphnia hyalina , 
the same as noted by Birgei (2b, p. 402). 
Daphnia pulicaria .—There was no movement of this species. 
Ceriodaphni-a .—This form was rare and showed no move¬ 
ment. 
