160 Thirty-fifth Annual Meeting 
covered with insect larvae which are lying in the mud and feed- 
ing on the lower organisms which live at all depths, and both 
insects and lower crustacea supply food for fishes. I think the 
true whitefish is found in fair numbers in this lake. Now our 
southern Wisconsin lakes lack oxygen in the bottom water; in- 
sect larvae, therefore, cannot live at the bottom. Oxygen is cut 
off from the lower water early in July and does not increase 
there again till October; and the result is that the bottom waters 
of our lakes are poor in life, and there is no possibility of rais- 
ing in these lakes those fish that must live in cool water and must 
find in the deeper parts of the lake a large supply of food and 
air. 
I have added another diagram (Fig. 12), showing the distri- 
bution of oxygen and temperature in Trout Lake, as found by us 
during the present season and which perhaps shows conditions 
a little like those of Walnut Lake. This lake has a depth of 
about 100 feet, with a length of about 4 miles, and a breadth of 
2.5 miles. It is in two parts, however, which are connected by a 
narrow opening only. The diagram is taken from the southern 
and larger portion, which is about 2 miles long, divided by is- 
lands into two or more basins. In this true whitefish (Coregon- 
us) and lake trout are found; the latter inhabiting the deep 
water during the summer. The diagram shows that although 
the oxygen declines in the lower and cooler water, it declines 
very slowly and that there is a considerable amount until the 
very bottom of the latter is reached. Down in the oxygen-poor 
water at the bottom lake trout are able to live, as our observations 
have shown. ‘There is a marked contrast between the oxygen con- 
tent of the lower water in this lake and that of any of the lakes 
of similar depth in Southern Wisconsin, and this difference is 
probably due to the very small amount of animal and vegetable 
life found floating in the open water of Trout Lake. Very few 
lakes in Northern Wisconsin have been examined carefully, but 
Trout Lake is the poorest in this respect of all the lakes which 
we have studied. 
The oxygen and other gaseous conditions of the water in gen- 
eral and of the bottom water in particular, are prime conditions 
of hfe, which determine not only the lower life but the possi- 
bilities of the higher life of the lake also; and for this reason I 
