Xlii FISHES OF ILLINOIS 



with its interstices filled with Lemnacece [duckweed] dotted with 

 the black statoblasts of Plumatella. From this dark labyrinth 

 we emerge to the muddy but quiet waters of Seeb's Lake with 

 its treacherous bottom of soft black ooze. We next enter a wider 

 stretch of more open territory with scattered willows and maples 

 and a rank growth of semiaquatic vegetation, principally Polyg- 

 onwns [heart- weed]. The water is clearer and of a brownish 

 tinge (from the diatoms) , while mats of algae adhere to the leaves 

 and stems of the emerging plants. A flock of startled water- 

 fowl leave their feeding grounds as we pass into the wide expanse 

 of Flag Lake. We push our way through patches of lily-pads 

 and beds of lotus, past the submerged domes of muskrat houses 

 built of last year's rushes, and thread our way, through devious 

 channels, among the fresh green flags and rushes just 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 Thompson'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 fish. Schools of young fry can be seen feed- 

 ing upon the plankton in the warm and quiet waters. Thomp- 

 son'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 

 towards the Illinois River, crossing the lower bottom-lands above 

 this region. If we push on through the fringing willows at the 



