790 Wisconsin Academy of Sciences, Arts, emd Letters. 
consisted of non-aquatic forms. Both adult aquatic insects 
and aquatic larvae of insects were important factors in the 
food of the small brook trout and the fry. 
Thirty-three specimens in all had eaten Crustacea. Of 
this number, twenty-six had eaten only Daphnias, one only 
Copepods, four both Daphnias and Copepods, and two only 
Gammari. The stomach of a greenback trout 30 centime¬ 
ters long contained about 4,500 Daphnias ; another contained 
2,250; and the stomach of a rainbow trout 38 centimeters long 
also contained about 1,300 Daphnias. A little more than six¬ 
teen per cent of the specimens examined which belonged to 
these two species of trout had eaten Daphnias , the number eat¬ 
en in each case varying from about 50 or 75 to 4,500. It is 
evident that they were very important factors in the destruc¬ 
tion of the Daphnia population of the lakes, for the lakes were 
well stocked with both of these trout, and the above figures rep¬ 
resent only the number of Daphnias consumed by each trout 
at a single meal. 
Two Mackinaw trout ( Cristivomer namaycush ) were ob¬ 
tained. One of the sp ecimens was 75 centimeter s long, a ad 
its stomach contained a trout 17.5 centimeters long and a few 
insect fragments. The stomach of the other specimen was 
empty. 
LAKE TAHOE. 
Lake Tahoe lies in eastern California and western Nevada. 
The boundary line between the two states passes through it in 
a north-south direction near its eastern shore, so that a little 
more than two-thirds of its area lies in California. The 
thirty-ninth parallel of latitude crosses the southern end of the 
lake. 
The lake occupies an elevated valley between two ranges of 
the Sierra Nevada mountains. Its surface is about 1,900 
meters above sea-level. The greatest length is about 36 kilo¬ 
meters and greatest width 20 kilometers. Its area is about 
500 square kilometers. Comparatively few soundings have 
been made in the deeper water, and the greatest known depth 
is 500 meters. The lake is surrounded by an amphitheater of 
