178 American Fisheries Society 



in such a situation would not be able to perform, and then 

 (4) to combine with these, of course, the determination 

 of the fundamental conditions of existence that are favor- 

 able and unfavorable for fish life. Naturally this study 

 concerns not merely the fish, but the smaller animals, 

 such as insects, etc., that constitute the food for the fish, 

 and also still other forms, like the microscopic organisms 

 which are so abundant in the complex of life, and so 

 important. 



