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perch and minnows. In its youngest stages the black bass was 
found to be a plankton (Hntomostraca) feeder, and later chang- 
ing to a fish diet. It is interesting to note that its principal 
fish food, young Dorosoma, is itself in its younger stages a 
plankton feeder, secondarily adopting a limophagous habit. 
The bottom slime thus eaten by the growing and adult Doro- 
soma is a food largely because it contains so many organisms 
normal or adventitious tothe plankton. Thus at all seasons the 
plankton forms an important link in the chain of food relations 
leading to the black bass. 
The buffalo-fishes and the German carp are likewise to a 
large degree dependent for food upon the plankton in early 
stages of growth, and, like Dorosoma, subsequently adopt the 
limophagous feeding habit. The organisms of the plankton 
thus at all times enter largely into the sources of their food 
supply. ‘The contents of the digestive tracts of these impor- 
tant food fishes examined by me at Meredosia during the 
spring months of 1899 were found uniformly to contain com- 
minuted vegetable debris, which constitutes the greater part of 
the unstable ooze or slime which abounds in the backwaters of 
the river, and, associated with this, many Hntomostraca, rotifers, 
rhizopods, and unicellular or colonial alge, belonging to species 
common in the plankton at that season of the year. The mori- 
bund, the spore-forming, the egg-laden organisms of the plank- 
ton sink to the deeper strata, and together with the normal 
denizens of the bottom slime, which are everywhere adventi- 
tious in our plankton, form the food of these fishes of greatest 
commercial importance. 
A very striking instance of the adaptation of the breeding 
seasons of fishes to food conditions is found in their nice ad- 
justment, for the most part, to the seasonal course of plankton 
production in our waters. Most of our minnows, the dogfish 
and gar, the Catostomide, the carp, Dorosoma, and the Etheosto- 
mide spawn in central Illinois during April and the first of May, 
while the bass, the sunfishes, and many of the Siluride follow 
in May. This brings the maximum number of young fish, re- 
