15a 



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 Lemnacece 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. 

 IL ) 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 {Auiia calva) and, if we are late enough in 

 the season, the myriads of young black, tadpole-like catfish 

 (Ameiio'us), likewise in schools, while young cs^rip {Cyprinus 

 carpio) are everywhere. The new vegetation is already spring- 



