The Food of the Smaller Fresh - Water Fishes. 
67 
the retreating overflow of streams, others from permanent lakes, 
and still others from creeks and rivers. The food from the differ- 
ent localities varies but little, on the whole, and it is scarcely 
worth while to discuss the separate collections. That of these 
nineteen specimens was almost purely animal, traces of a minute 
flowering plant (Wolffia), and small quantities of filamentous 
Algae only being taken by two of the specimens. Fishes were 
eaten by but two, and were reckoned at two per cent, of the 
food of the whole. One of these found was recognizable as a 
Oyprinoid, but the other could not be determined. Insects 
amounted to more than ninety per cent., all of them aquatic, with 
the exception of a few gnats (Culicidae) taken by eight of the 
fishes. Nearly half of the food consisted of larva? of Chirono- 
mus and Corethra. Aquatic coleopterous larva? were reckoned at 
eleven per cent., and specimens of Corixa, taken by three of the 
fishes, at two. A single fish had also eaten Galgulus. A fourth 
of the food consisted of neuropterous larvae (Ephemeridae and 
Libellulidae). Crustaceans, though captured by more than half 
the fishes, made but four per cent, of the food. As far as recog- 
nized, this element consisted chiefly of the amphipod, Allorchestes 
clentata , and the common isopod, Asellus. A few specimens of 
Cyprididae were noticed in two of the fishes, and Cyclops and 
other Copepoda were taken by five. One fish had eaten a 
Lumbri oulus, a species closely allied to the common earthworm. 
A careful comparison was made of the food of specimens of 
various ages — those, consequently, in which the situation of the 
vent was widely different — but no differences of food whatever 
were distinguishable. It is highly probable, consequently, that the 
explanation of this peculiar character must be sought elsewhere 
than in the food. With respect to the other relation^ of food to 
structure, we have at present only to note the coincidence of fishes 
and aquatic insects as the principal elements of the food with the 
large mouth and inferior development of the gill and pharyngeal 
apparatus, and short and simple intestine. 
FAMILY COTTIDiE. 
This curious family, chiefly marine, is represented in the State 
by several species from Lake Michigan, mostly from its deeper 
waters, and by a single one recently discovered in our streams. 
