88 American Fisheries Society 



If I remember correctly, Mr. Titcomb referred to the habit of certain 

 persons cooking mixed foods containing a certain amount of plant material 

 or grains. You will, many of you, who have attended these meetings for 

 some years, recall the experiments of our dear friend, Professor Dyche, of 

 Kansas, in raising fish on grain in the experimental fish ponds of that state. 

 Now it is a very fair question to ask whether, if you were to attempt to 

 utilize a food of the solid type of grain, or of the condensed sort of vegetable 

 foods, some cooking is not necessary in order to make it possible for the 

 fish to utilize it, and whether the lack of utilization found in some experi- 

 ments, is not due to the lack of mere softening to put the food in such con- 

 dition that the digestive processes can be carried out and the material 

 utilized. You see the experiments there differ very radically from those 

 on which Professor Morgulis was engaged. 



The ultimate question in future will have two elements also, first, its 

 degree of utilization, which Professor Morgulis has treated here quite 

 carefully for individual foods; and, second, its cost. If half as much of one 

 food is utilized, and that food would only cost one-third as much, it still 

 might be the better food to use. The question of the degree of utilization 

 once for all concludes the problem for the fish culturists of what kind of 

 food should be used in practical work. 



And then there is a third question, and that is the effect of mixed diet, 

 for we know very well by animal experimentation in other cases that feeding 

 with a single food substance and feeding with a mixture of food materials, 

 are accompanied by quite different relative results, and the amount of 

 material utilized in a mixture may be quite different from the amount of 

 some material which is used and results obtained in feeding with a single 

 type of food. This concerns not merely different kinds of animal food, but 

 also a mixture of animal plant food, and Prof. Embody had some very 

 interesting suggestions concerning a mixture of different kinds of animal 

 food. Of course I mention that here, not to contribute anything to the 

 knowledge of the subject, but perhaps to keep some of you from drawing 

 indirect conclusions from this or some other paper. Feeding with a single 

 substance will show one element in the problem. It will not decide, how- 

 ever, the relative advantage of that substance over any other single sub- 

 stance, until the mixture has been tested. Until the question of mixtures as 

 different as those of animal and plant food be tested, and until the question 

 of cooking be tested on plant material, and all of these tests averaged with 

 the cost, the man who wants to feed his trout cannot tell finally what is 

 the most efficient food, that is, the food which can be fed at the least cost, 

 and the best results secured. 



A Study of the Effects of Certain Oils, Tars and Creosotes Upon 

 Brook Trout (Salvelinus Fontinalis). 



BY ADRIAN THOMAS. 



This paper, with the discussion, appears later in this issue of 

 the Transactions, page 121. 



