The Lake as a Microcosm. 81 
And now if you will kindly let this suffice for the background or setting of 
the picture of lacustrine life which I have undertaken to give you, I will next 
endeavor —not to paint in the picture—for that I have not the artistic skill— 
but I will confine myself to the humbler and safer task of supplying you the 
pigments, leaving it to your own constructive imaginations to put them on 
the canvas. 
When one sees acres of the shallower water black with water-fowl, and so 
clogged with weeds that a boat can scarcely be pushed through the mass; 
when, lifting a handful of the latter he finds them covered with shells and alive 
with small crustaceans; and then, dragging a towing net for a few minutes, 
finds it lined with myriads of diatoms and other microscopic Algae, and with 
multitudes of Entomostraca, he is likely to infer that these waters are every- 
where swarming with life, from top to bottom, and from shore to shore. If, 
however, he will haul a dredge for an hour or so in the deepest water he can 
find, he will invariably discover an area singularly barren of both plant and 
animal life, yielding scarcely anything but a small bivalve mollusk, a few low 
worms, and red larve of gnats. These inhabit a black, deep, and almost 
impalpable mud or ooze, too soft and unstable to afford foot hold to plants, 
even if the lake is shallow enough to admit a sufficient quantity of light to 
its bottom to support vegetation. It is doubtless to this character of the 
bottom that the barrenness of the interior parts of these lakes is due; and this 
again is caused by the selective influence of gravity upon the mud and detritus 
washed down by rains. The heaviest and coarsest of this material necessarily 
settles nearest the margin, and only the finest silt reaches the remotest parts of 
the lake, which, filling most slowly, remain, of course, the deepest. The 
largest lakes, are not, therefore, as a rule by any means the most prolific of life, 
but this shades inward rapidly from the shore, and becomes at no great distance 
almost as simple and scanty as that of a desert. 
Among the weeds and lily-pads upon the shallows and around the margin, 
the Potamogeton, Myriophyllum Ceratophyllum, Anacharis and Chara, and 
the common Nelumbium—amoug these the fishes chiefly swim or lurk, by far 
the commonest being the barbaric bream or “pumpkin seed” of northern 
Illinois, splendid with its greens and scarlet and purple and orange. Little 
less abundant is the common perch (Perca lutea), in the larger lakes,—in the 
largest outnumbering the bream, itself. The whole sunfish family, to which 
the latter belongs, is, in fact, the dominant group in these lakes. Of the one 
hundred and thirty-two fishes of Illinois only thirty-seven are found in these 
waters—about twenty-eight per cent.—while eight out of our seventeen sun- 
fishes have been taken there. Next, perhaps, one searching the pebbly beach- 
es, or scanning the weedy tracts, will be struck by the small number of min- 
nows or cyprinoids which catch the eye, or come out, in the net. Of our 
thirty-three Illinois cyprinoids, only six occur there — about eighteen per cent. 
—and only three of these are common. ‘These are in part replaced by shoals 
of the beautiful little silversides (Labidesthes sicculus) a spiny-finned fish, 
bright, slender, active, and voracious —as well supplied with teeth as a perch, 
and far better equipped for self-defense than the soft-bodied, and toothless 
cyprinoids. Next, we note that of our twelve catfishes only two have been 
taken in these lakes,—one the common bullhead (Jetalurus nebulosus) which 
occurs everywhere, and the other an insignificant stone cat, not as long as 
one’s thumb. The suckers, also, are much less abundant in this region, the 
buffalo fishes not appearing at all in our collections. Their family is repre- 
sented by the worthless carp, by two redhorse, by the carp sucker and the 
common sucker (Catostomus commersonii), and one other species. Even the 
hickory shad — an ichthyological weed in the Illinois— we have not found in 
these lakes at all. The sheepshead, so common here, is also conspicuous there 
by its absence. The yellow bass, not rare in this river, we should not expect 
