REACTIONS OF FISHES TO SALTS 281 



to hydrogen and hydroxjd ion.s. The reactions to either the ions 

 of salts or acids are compHcated by the presence of the ions of 

 the other. 



3. Fresh water fishes react to combinations of antagonistic 

 salts or to an antagonistic salt and acid, in a way that tends to 

 bring them into a region of optimum stimulation. The phe- 

 nomena of antagonism are thus indicated by the behavior as well 

 as the resistance of organisms. 



4. Starvation causes certain fishes (e.g., Ambloplites rupestris, 

 rock bass) to select higher concentrations of salt than those 

 normally selected. Other fishes (Ameiurus melas, bull-head) 

 when starved, select lower concentrations than normally. Over- 

 feeding causes bull-heads to select higher concentrations, than 

 those normally chosen. 



5. Rock bass and bull-heads which are normally negative to 

 CaCls O.OIN solution, become positive after being kept in this 

 concentration for about a week. They become negative again 

 when returned to tap water for 24 hours. 



6. The migrations of anadromous fishes are probably corre- 

 lated with rhythmic changes in metabolism. These alterations 

 in metabolic activity are largely the result of internal changes 

 such as occur with the ripening of the sexual products. 



I am indebted to Prof. A*. E. Shelf ord for proposing this prob- 

 lem and for many suggestions during the work. I am also under 

 obhgation to Air. Karl A. Clark of the Chemistry Department 

 for helpful criticisms and for the loan of apparatus. 



