153 
emerging from the water. Open patches of water here and 
there mark the areas occupied by the “moss” or Ceratophyllum, 
as yet at some depth below the surface. The Lemnacee are 
everywhere lodged in mats and windrows, and, amidst their 
green, one occasionally catches sight of a bright cluster of 
Azolla, The water is clear and brownish save where our 
movements stir the treacherous and mobile bottom. We now 
enter a second time the partially wooded country, and cross 
the submerged ridge to the sandy eastern shore of Thomp- 
son’s Lake. This ridge is covered by submerged vegetation 
which has as yet attained but little growth. The “breaks” of 
the startled fish show that we have invaded favorite feeding 
grounds. The waters are evidently moving towards the river, 
and they bear the rich plankton of Thompson’s Lake, while 
their turbidity is doubtless increased by the movements of the 
tish. Schools of young fry can be seen feeding upon the 
plankton in the warm and quiet waters. Thompson’s Lake, 
the largest expanse of water in the neighborhood, is wont to be 
rough in windy weather, but if the day be still we can see the 
rich aquatic vegetation which fringes its margin and lies in 
scattered masses toward its southern end. Its waters seem 
somewhat turbid, but more from plankton than from silt, 
though the deep soft mud which forms much of its bottom is 
easily stirred. The slender transparent limnetic young of the 
gizzard-shad may be seen swimming near the surface. There 
is a perceptible drift to the south in the open lake, though this 
current is deflected by the elevated banks of Spoon River ( PI. 
II.) towards the Illinois River, crossing the lower bottom-lands 
above this region. If we push on through the fringing willows 
at the south we find a series of open places locally known as 
“ponds”. The warm still waters are turbid in places from the 
- movements of fish, and at times we see the compact schools 
of young dogfish (Amia calva) and, if we are late enough in 
the season, the myriads of young black, tadpole-like catfish 
(Ameiurus), likewise in schools, while young carp ( Cyprinus 
carpio) are everywhere. The new vegetation is already spring- 
