141 



which it depends for subsistence, and so finally indirectly cripple 

 itself. Then the money and labor expended in its culture would 

 be worse than the first. An acquaintance with the food of the young 

 is especially necessary, because they are planted by the fish-culturist 

 when, having already absorbed the egg-sac (the supply of food by 

 which they are under natural conditions supported until they have 

 time to scatter themselves widely through the water), they are in a 

 peculiarly helpless condition, unable to wander far in search of sub- 

 sistence, and compelled to find food speedily or perish. One would 

 say, therefore, that their alimentary resources and habits should be 

 well and thoroughly known, that the range, period, and abundance 

 of the organisms upon which they feed sliould be carefully deter- 

 mined, and that each locality where the young are deposited should 

 be closely searched for the purpose of ascertaining whether their 

 food species occur there at the time in sufficient quantity to prevent 

 immediate starvation. 



Previous studies of the food of young fishes of a variety of fam- 

 ilies, reported in the third Bulletin of this series, had showed that, 

 with exceptions presently to be mentioned, the earliest food of all 

 families st idied consisted almost wholly of various species of 

 Entomostraca and some equally minute and delicate dipterous larvse. 

 When that paper was prepared, I had, however, no opportunity to 

 study the food of the young of any members of the Salmonid^e, to 

 which the white-fish belongs, neither could I learn that any such 

 studies had been made by others ; and I could only infer the same 

 fact with regard to this family from the general character of the results 

 obtained by the study of the other groups. Even this inference, however, 

 was rendered doubtful by the discovery that the youngest individuals of 

 two of the toothless families (Catostomidae and Cyprinidse) were not 

 strictly dependent upon the food elements above mentioned, but 

 were likewise able to draw upon much smaller organisms; namely, 

 the minutest Protozoa and unicellular Alga ; and as the adult white- 

 fish is likewise destitute of teeth, it was not by any means certain 

 that their young would not fall under the latter category. Upon 

 looking up the literature of the subject, I found that although the 

 food of the adult had been very well made out in a general way,* 

 only two items had been published respecting the food of the young. 

 In the report of the United States Fish Commission for 1872-73, an 

 assistant commissioner, Mr. J. W. Milner, made some experiments 

 on young white-fish hatched artificially, supplying them with a num- 

 ber of articles of food, in the hope of finding something suitable for 

 their nourishment. 



"A few crawfish," he says, "were procured and pounded to a paste, 

 and small portions put into jar No. 1 ; the young fish ate it readily. 

 They were fed at night, an. I the next morning every one of them 

 was found to be dead. Jar No. 2 was supplied with bread crumbs, 

 and the fish were seen to take small particles in their mouths ; they 

 did not die so suddenly. Jar No. 3 was supplied with sweet cream, 

 but no evidence was afforded that the occupants fed upon it. A 

 quantity of rain-water was exposed to the rays of the sun for the 

 purpose of generating minute forms of life, and a teaspooful was 



* Report of tht' U. S. Fish (\>mmission for 1872-73, i>p. 44-46. 



