488 Illinois State Lahoratorij of Natural History. 



again, the smallest forms were the most abundant. Generally, 

 however, the Cladocera were more common than the other 

 orders, the bivalve Cypris (most frequent in the mud) being 

 much less abundant in the food. I have shown elsewhere,* at 

 length, that Entomostraca compose by far the greater part of 

 the food of young fishes of all descriptions, — with the partial 

 exception of the sucker family, the young of which feed largely 

 on still more minute organic forms, — and present an abstract 

 of these facts in this article under another head.f 



Particulars concerning the use of this abundant and varied 

 group as food for fishes, are so numerous as to make them diffi- 

 cult to summarize, and the interested reader is again referred 

 to the detailed list accompanying this paper. 



VERMES AS FOOD FOR FISHES. 



Probably to those accustomed to the abundance of true 

 worms (Vermes) in marine situations, no feature of the poverty 

 of fresh-water life will be more striking than the small number 

 of this subkingdom occurring in the course of miscellaneous 

 aquatic collections in the interior. Similarly we notice that in 

 the food of fishes the occurrence of Vermes is so rarely noticed 

 that they might be left out of account entirely without appre- 

 ciably affecting any of the important ratios. 



The minnows (cyprinoids) had eaten more of them than 

 any other family, — three per cent, of the food of twenty-two 

 specimens of Semotilus being credited to them, and one per 

 cent, of that of thirteen specimens of Pimephales, besides a 

 trace in the food of Notropis. More precisely analyzed, we 

 find that a single Nais, a Lumbriculus, two examples of Gordius 

 (doubtless taken as insect parasites) and several minute roti- 

 fers (wheel-animalcules) are the forms upon which this esti- 

 mate is based. 



A trace of Vermes likewise appears in the food of suckers, 

 — mostly a polyzoan species (Plumatella) and minute rotifers 

 sucked up with the mud. 



* Bull. 111. St. Lab. Nat. Hist, Vol. I., No. 3, pp. 75, 76. 

 t See pp. 495 and 496. 



