of Fresh-Wafer Fishes. 493 



(Pomoxys) from three quarters of an inch to an inch and a 

 half, and six indeterminable specimens, probably Lepomis, from 

 seven sixteenths to five eighths of an inch long. A single 

 sheepshead an inch and an eighth in length had eaten Chiron- 

 omus larvae (seventy-five per cent.) and larvae of the u river 

 fly" (Hexagenia). A single grass pickerel about an inch and 

 a quarter long had taken about sixty per cent, of its food from 

 Entomostraca and young Amphipoda, the remainder consisting 

 of little fishes. 



The first food of the common white-fish was determined 

 experimentally, the breeding habits of this species making 

 direct observation impossible. Three hundred and forty very 

 young fry fed with fragments of the brook shrimp, Gammarus, 

 in a hatching house, were examined in January, 1881, and 

 thirty-five of them, which had apparently taken food, were dis- 

 sected. Minute fragments of Gammarus were found in but 

 eighteen of these, while five contained minute insect larvae, 

 four, Entomostraca, and eight, small particles of vegetation, 

 objects accidentally conveyed to them in the water of the 

 hatching house. In two hundred and forty-two others, con- 

 fined in spring water; only eight were found to have eaten 

 anything, and these had taken only Algae and vegetable frag- 

 ments. In February of the same year, fourteen specimens, 

 confined in a small aquarium and supplied with living objects, 

 plant and animal, from stagnant pools, were proven to feed 

 freely upon the smallest Entomostraca presented to them, 

 chiefly Cyclops and Canthocamptus, ten of the fourteen eating 

 Cyclops, three Canthocamptus, and one a specimen of each. 



A little later, a more extensive experiment was conducted 

 by means of a large aquarium, in which there were placed sev- 

 eral hundred fry, kept constantly supplied with all the living 

 objects which a fine gauze net would separate from the waters 

 of Lake Michigan. Of one hundred and six of these, dissected 

 within the following fortnight, sixty-three had taken food con- 

 sisting almost wholly of the smallest Entomostraca occurring 

 in the Lake (a minute Cyclops and a slender Diaptomus). 

 The other objects encountered were rotifers, and diatoms and 

 other unicellular Algae, appearing, however, in such trivial 

 quantity as to contribute nothing of importance to the sup- 

 port of the fry. 



