ij REPORT OF THE STATE ENTOMOLOGIST 1907 181 
Diatoms in a considerable variety, filaments of Cyanophyceae and 
Desmids (among which the genera Closterium and Desmidium were 
recognized). All of these occurred sparingly and may very well 
have been taken along with the disintegrating stems and leaves of 
the higher plants. 
This last mentioned material was in four cases a mass of leaf 
fragments of a slender species of river weed (Potamogeton) and 
in three other cases it contained (once in excess) remains of the 
petiole of the yellow water lily (Nymphaea advena). These 
were recognizable by the well preserved internal hairs from the 
walls of the air chambers. Such food stuff was, of course, very 
abundant in this place. There may have been a good many other 
plants present, indeed [ have no doubt there were some others; for 
a form of tracheids quite unknown to me, derived from the vas- 
cular bundles of some other seed plant, occurred three times. 
These were the predominating elements of the food, however ; 
they show that at this time and place Chrosomus was a vegetable 
feeder. Apparently this singularly beautiful and hardy little fish 
is one that can be introduced safely into private ponds. 
I hasten to place beside the foregoing, the results of a more ex- 
tensive study of the food of this fish, made in quite a different 
situation, and so different in kind that they will teach the neces- 
sity of great care in reaching conclusions as to what fishes eat. 
A former pupil of mine, Mr Warren H. Ferguson, studied the 
food and feeding habits of Chrosomus in Pettibone creek, near 
North Chicago, Ill., in 1904. The place has since become the site 
of the United States Naval training station of the Great Lakes. 
The creek was then a beautiful little stream flowing through fine oak 
woods with here and there a deep shadowy pool and with inter- 
vening stretches of flowing water. It was one of my favorite 
collecting grounds when I lived at Lake Forest, 6 miles distant. 
A few other fishes live in the stream; the horned dace, a little 
stickleback, several darters, and very small suckers, but none were 
so abundant as Chrosomus; and only the darters that live in the 
riffles were as constantly to be found in a given place. 
The forage offered by this creek was very different indeed from 
that of Old Forge pond. Here there were no standing aquatics 
and no unattached filamentous algae. Rocks and sticks exposed 
in the riffles were draped with two beautiful sessile algae (Dra- 
pernaldia plumosaand a species of Cladophora). The out- 
let of every pool was choked, and every obstruction was covered 
