The Food of the Smaller Fresh - Water Fishes. 69 



Four specimens from llock River, tuid one from Cedar Lake, in 

 Lake County, had divided their food about equally between plant 

 and animal substances: tlie former, consistintr wholly of filamen- 

 tous Alg;v, taken by four of the specimens in quantities to make 

 it certain that they were ingested purposely. The animal food 

 was about equally insects and crustaceans, the former nearly all 

 aquatic larv;\? of Diptera (Chironomus being the commonest form), 

 and the latter chiefly Entomostraca, of which Cladocera were the 

 most abundant. One of the specimens had eaten Cypris — some 

 of them Ct/pn's vidua. Cyclops was also noticed in three of the 

 fishes, and amounted to three per cent, of the food. 



The herbivorous character of this fish seems not to be related to 

 any structural facts; but the occurrence of the large ratio of En- 

 tomostraca is at once accounted for by the well-developed gill- 

 rakers, these serving as a straining apparatus by means of which 

 the fishes possessed of it are able to appropriate minuter organ- 

 isms than would otherwise be available for their food. 



Pygosteus pungitius, Lac. Many-Spined Stickleback. 



This species has hitherto been found by us only in Lake Michi- 

 gan, and in Calumet River near its mouth. 



But two specimens were dissected; and these had fed wholly 

 on larvaj of Chironomus and Simulium (sixty per cent.), and on 

 Chydorus and other Cladocera (forty per cent.). 



With so small an amount of material to illustrate the food of 

 the family, we can only say that it evidently consists chiefly of 

 aquatic larva? and Entomostraca, together with a considerable per- 

 centage of vegetable substances. In the absence of any appara- 

 tus for mastication, the latter will doubtless be found to consist of 

 Alg<e, as in the cases examined. 



FAMILY ATHERINID^. 

 Labidesthes sicculus, Cope. Silversides. 



This elegant little fish, the only fresh-water representative of 

 its family, is generally abundant throughout the State, and has 

 been collected by us in a great variety of situations, from the 

 northern lakes to the Wabash River. 



It is long and slender, the mouth small and well furnished with 



