450 Illinois State Laboratory of Natural History. 



when it made in some cases as high as ninety-five per cent. 

 The larger duckweed (Lemna), fragments of Ceratophyllum, 

 diatoms, and other unicellular Algae, are also worthy of men- 

 tion. 



The animal food (eighty per cent.) was fairly well divided 

 between Mollusca, insects, and Crustacea, respectively thirty, 

 twenty-nine, and twenty per cent. Only occasional traces of 

 univalves were noticed (Vivipara and Planorbis); but the thin- 

 shelled bivalve Sphaerium was a very important element, taken 

 by seven of the fishes, and reckoned at thirty per cent, of the 

 food of the group. Several individuals had eaten nothing else. 



Insect larvae were very generally taken, and, in fact, oc- 

 curred in the food of every specimen examined. Chironomus 

 larvae were reckoned at nearly a fifth of the food, and were 

 found in fourteen out of the seventeen fishes. Neuroptera 

 larvae, on the other hand, occurred in relatively insignificant 

 number, most of them Ephemeridae ; although a small num- 

 ber of case-worms (Leptocerus) and of dragon-fly larvae 

 ( Agrion) were also noticed. Hydrachnida occurred in the food 

 of one, and Crustacea were eaten by thirteen specimens, all 

 Entomostraca with the exception of a single small crayfish 

 and an amphipod. 



Curiously, the entomostracan eaten most freely by these 

 large fishes was the smallest of the Copepoda Canthocamptus. 

 In the food of ten specimens taken at Peona April 16, 1880, 

 and October 6, 1887, this made nineteen per cent, of the food 

 of the entire group. Specimens of Cyclops, Cypris, Pleuroxus, 

 Iliocryptus, Bosmina, and Simocephalus occurred in numbers 

 too small to figure in the ratios. Fresh-water Vermes were 

 almost wholly wanting, only a few Anguillulidae occurring in 

 the food of one. Eight had eaten Polyzoa, including both 

 Plumatella and Pectinatella. The latter was recognized by 

 its statoblasts only, detected in seven specimens collected in 

 October, 1887, in situations where the gigantic colonies formed 

 by this polyzoan had been earlier very abundant. It is proba- 

 ble, consequently, that these statoblasts, widely dispersed with 

 the death and decay of the translucent mass in which they are 

 developed, had been picked up by accident with the other food.* 



* Some notes on the young of this genus, published in the Bulletin 

 of this Laboratory, Vol. I, No. 3, page 73, show that specimens varying 



