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THE AMERICAN NATURALIST [Vol. LII 



few scattered plants of the seven-angled pipewort may 

 be seen. Ordinarily the stream habitat furnishes the 

 most favorable ground for vegetation, yet we see in these 

 streams a dearth of species and a limited growth that 

 clearly indicates limited and restricted food for such ani- 

 mals as live upon aquatic plants. 



The barren sandy-shoal, the barren stony-shoal and the 

 deep-water habitats are each almost entirely free from 

 plant life. This leaves the vegetative to supply the neces- 

 sary food. Aside from two patches of bullrushes and two 

 small groups of yellow lilies, the vegetative habitat is re- 

 stricted to the plants that form on the slope leading to 

 the fifteen-foot contour. At station 12, for possibly an 

 eighth of a mile, there is a thick fringe of aquatic plants 

 composed of Potamogeton prealongus and robbinsii. In 

 the southeastern part of the lake and also near station 8 

 two other thick areas of plants occur. These consist of 

 Potamogetons, with the addition of a third species, P. 

 oakesiamis. Of the possible four miles of this slope 

 around the lake not more than one sixth supports plants. 



The study of these habitats then shows that the fish 

 are limited to the vegetative habitat in their search for 

 such food as lives in turn upon aquatic plants. 



In order to determine what the fish were actually living 

 upon, a study of the stomach contents was made, of which 

 the following is a summary: 



Salvelinus fontinalis Mitchill. Brook Trout.— The 

 black-striped minnow {Leu-ciscus carletoni), grasshop- 

 pers, crayfish, snail {Campeloma decisa), a few insect 

 larvae and a pumpkin seed made up the diet of the twenty 

 stomachs examined. 



Eupomotis gibbosus Linnaeus. Pumpkin seed. Col- 

 lected at station 8, 20 to 25 mm. long.— Daphnia and 

 cyclops with an occasional insect larva. Fish of the same 

 size from station 5 were feeding entirely upon daphnia 

 and cyclops. Judging from the number found in some 

 of these fish, I would estimate that these small fish must 

 eat more than 1,000 Crustacea daily. One specimen had 



