72 The Food of Young Fishes. 



ity of food was noticed among species and families whose 

 later food-habits are widely different. 



The full-grown black bass, for example, feeds princi- 

 pally on fishes and crawfishes, the sheepshead on mollusks, 

 the gizzard-shad on mud and Algse, while the catfishes are 

 nearly omnivorous ; yet these are all found to agree so 

 closely in food when very small that one could not possibly 

 tell from the contents of the stomachs which group he 

 was dealing with. 



It is my purpose in this paper to give what facts I have 

 relating to the food of our fresh-water species during this 

 first period of the fish's life. These facts were derived 

 from the examination of one hundred and twenty-six spec- 

 imens, ranging from three-eighths of an inch in length up 

 to an inch and a half, and in a few cases to two and three 

 inches. These specimens belong to twenty-four genera 

 and represent eleven families. In two or three genera 

 none were obtained small enough to be regarded as be- 

 longing strictly to this first food-period, but the earliest 

 food is nevertheless plainly inferable ; and the general 

 distribution and variety of the species studied is such that 

 I think the main conclusions will be found to stand the 

 test of full investigation. .As the first period is evidently 

 much shorter with some species than with others, and 

 doubtless varies in the same species according to situation 

 and circumstances generally, of course no common limit of 

 size could be set up, but the smallest specimens of each 

 species were selected until a size was reached where a 

 marked difference of food appeared. 



ACAKTHOPTERI. 



Although the young Acanthopteri have already been dis- 

 cussed in the preceding paper on the food of that group, it 

 will be convenient to review the facts concerning these 

 young fishes for the purpose of comparing their food with 

 that of the other orders. 



The food of six common perch {Perca americana)^ from 

 an inch to an inch and a quarter long, consisted wholly of 

 Entomostraca and larvse of Chironomus, — eight per cent. 

 Chironomus, fifty-two per cent. Cladocera, and forty per 

 cent. Oopepoda. 



