183] FAUNA OF BIG VERMILION RIVER—BAKER 85 
It seems evident that this portion of the old stream forms a reservoir 
from which certain species of mollusks, as well as fish, are carried, or volun- 
tarily migrate, through the outlet into Salt Fork. By this means only 
can the presence of these animals in the polluted water be accounted for, 
because none have been seen either above or far below the drain from the 
old stream channel. The specimens of Planorbis trivolvis, that have been 
observed in the Salt Fork canal below the east and west road bridge, were 
probably derived from this source. 
Specimens of Planorbis trivolvis have been observed in the Salt Fork 
canal which probably came from this source. Near this locality a school 
of about fifty fingerling bullheads was observed on May 29, in a small 
part of the stream where a rather deep pool had developed. They were 
making frantic efforts to get out of the pool but the surrounding water 
was too shallow. The low water and general polluted condition of the 
stream evidently provided a very unfavorable environment. The source 
from which these fish came was quite likely the old cut off portion of the 
original Salt Fork from which place they had been carried or had volun- 
tarily migrated, when the water was higher from the April rains. 
From the east and west road bridge (Fig. 45) to the first farmer’s bridge, 
a distance of about three-quarters of a mile, the conditions are the same 
as in the preceding portion of the canal. The water is clear but no living 
mollusks or other animals could be found. A half valve of Anodonta 
grandis, badly weathered, and a few bleached valves of Sphaerium solidu- 
lum, were the only evidences of molluscan life. These had evidently been 
washed from the old stream bed at some point where it was exposed by 
erosion in the canal walls. The same algae as previously observed was 
floating down the stream in large green patches. Samples of these green 
particles were examined by Professor Smith and found to contain such 
animals as Euglena geniculata, Paramoecium, and numerous ciliate Pro- 
tozoa, mostly inhabitants of polluted water. 
From the next farmer’s bridge to the eastward turn of the stream the 
bottom conditions were also similar, except that the surface of the water 
was covered with an oily scum. Groups of greater or less size of gyrinid 
beetles (Dineutes assimilis) were seen at different places down stream for 
a mile or more. A single empty shell of Planorbis trivoluis was observed 
on the shore of the west bank below this bridge. No living clams were 
seen, nor any mutilated valves. 
From the eastward turn of the stream to the mouth of Spoon River, 
the canal is in bad condition, the water being dirty and oily, with numer- 
ous bubbles of gas rising constantly from the bottom, which also gave off 
quantities of oily scum when disturbed (Fig. 44). The water is shallow 
and conditions as already described for the stream higher up. Green 
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