82 The Lake as a Microcosm. 
in these lakes, because it is rather a southern species; but why the white bass, 
abundant here, in Lake Michigan, and in the Wisconsin lakes, should be 
wholly absent from the lakes of the Illinois plateau, Iam unable to imagine. 
If it occurs there at all, it must be rare, as I could neither find nor hear of it. 
A characteristic, abundant, and attractive little fish is the log perch (Per- 
cina caprodes),— the largest of the darters—slender, active, barred like a 
zebra — spending much of its time in chase of Entomostraca among the water 
plants, or prying curiously about among the stones for minute insect larve. 
Six darters in all, out of the eighteen from the state, are on our list from these - 
lakes. The two black bass are the popular game fishes — the large-mouthed 
species being much the most abundant. The pickerels, gars, and dog-fish are 
there about as here, but the shovel fish does not occur. : 
Of the peculiar fish fauna of Lake Michigan — the burbot, white fish, trout, 
lake herring or cisco, etc., not one species occurs in these smaller lakes and all 
attempts to transfer any of them have failed completely. The cisco is a nota- 
ble fish of Geneva Lake, Wisconsin, but does not reach Illinois except in 
Lake Michigan. It is useless to attempt to introduce it, because the deeper © 
areas of the interior lakes are too limited to give it sufficient range of cool 
water in midsummer. 
In short, the fishes of these lakes are substantially those of their region,— 
excluding the Lake Michigan series (for which the lakes are too small and 
warm) and those peculiar to creeks and rivers. Possibly the relative scarcity 
of catfishes is due to the comparative clearness and cleanness of the waters. I 
see no good reason why minnows should be so few, unless it be the abundance 
of pike and Chicago sportsmen. . 
Concerning the molluscan fauna, I will only say that it is poor in bivalves 
—as far as our observations go—and rich in univalves. Our collections have 
been but partly determined, but they give us three species of Valvata, seven 
of Planorbis, four Amnicolas, a Melantho, two Physas, six Limneas and an 
Ancylus among the Gasteropoda, and two Unios, an Anodonta, a Spherium 
and a Pisidium among the Lamelli branchiates. Pisidiwm variabile is by far 
the most abundant mollusk in the oozy bottom in the deeper parts of the 
lakes; and crawling over the weeds are multitudes of small Amnicolas and 
Valvatas. | 
The entomology of these waters I can merely touch upon, mentioning only 
the most important and abundant insect larve. Hiding under stones and 
driftwood, well aware, no doubt, what enticing morsels they are to a great 
variety of fishes, we find a number of species of Ephemerid larvee whose speci- 
fic determination we have not yet attempted. Among the weeds are the 
usual larvee of dragon flies—Agrionina and Libellulide, familiar to every one; 
swimming in open water the predaceous larve of Corethra; wriggling through 
the water or buried in the mud the larve of Chironomus— the shallow water 
species white, and those from the deeper ooze of the central parts of the lakes, 
blood red and larger. Among Chara on the sandy bottoms are a great number 
and variety of interesting case worms — larvee of Phryganeidz — most of them 
inhabiting tubes of a slender conical form made of a viscid secretion exuded 
from the mouth and strengthened and thickened by grains of sand — fine or 
coarse. One of these cases, nearly naked, but usually thinly covered with 
diatoms, is especially worthy of note, as it has been reported nowhere in this 
country except in our collections, and, was, indeed, recently described from 
Brazil as new. Its generic name is Lageno-psyche, but its species undeter- 
mined. ‘These larvee are also much eaten by fishes. 
Among the worms we have of course a number of species of leeches and of 
planarians,— in the mud minute Anguillulide, like vinegar eels, and a slender 
Lumbriculus, which makes a tubulur mud burrow for itself in the deepest 
water, and also the curious Nais probiscidia — notable for its capacity of mul- — 
tiplication by transverse division. | 
