70 
as an estimate of the ratio of weeded to total area. In July or August, 
1920, two per cent. would have meant about 100 acres of vegetation in 
Thompson at the height of the growth period, while as a matter of fact 
a careful examination of the lower two-thirds of this lake, which was 
weedier than the upper third five to seven years ago, disclosed less than 
two acres that could be called even partially weedy. Over a total of 
some thousands of acres in these four lakes since 1913—1915, the plants 
have disappeared as completely as dry stubble before a fire, and our 
observations in Peoria Lake and reports from fishermen and other river 
men concerning lakes that we have not entered since 1915 indicate that 
the destruction has been little if any less complete everywhere in the back- 
waters between Chillicothe and Havana. 
In the scattered remnant-bunches of Potamogeton pectinatus still 
growing in Thompson Lake on the small sandy area of bottom at 
Warner’s Cut in September, 1920, it was impossible to collect by the 
quantitative method used in 1914 and 1915. It is, however, clear that 
the former enormous weed-animal yields—over 2000 pounds per acre 
for 40 to 50 per cent. of the total lake and pond acreage in this district 
six or seven years ago—have vanished with the water plants, and that 
any figures that could have been obtained last year by any method would 
stand as wholly negligible in comparison with the old averages. Unless, 
in fact, we assume, as is probably the case, that in the spring and earlier 
summer months there is at least a somewhat greater variety and abun- 
dance both of bottom and shore animals than was shown by the examina- 
tions made in September, 1920, it is hard to understand how the surviving 
food and game fishes that find their principal food in the small inverte- 
brate fauna can continue to subsist without evident general emaciation. 
Both the fact that they were not yet generally emaciated in the summer 
of 1920, and the very low indicated residues of bottom and shore animals 
after six or seven months feeding at the same time may, from another 
view-point, be taken as evidence that the food supplies are in recent 
seasons being fed down to an unusually low point before autumn; or, 
in other words, that the heavy declines in midsummer valuation-figures 
of all small bottom-animals since 1915 may not be quite so altogether an 
effect of the advance of sewage pollution as are the indicated changes in 
the composition of the fauna. 
Stewart Lake, an all-Bottom-land Lake of the Shallower Type, 
twenty Miles south of Havana 
(Mile 224.0—226.0 below Lake Michigan) 
The first impression one receives upon going into Stewart Lake and 
handling samples of its muds, after a week of work in the barren ex- 
panses of gas-filled lake and river floor twenty miles north, is one of 
large and distinct improvement in the odors and physical appearance of 
