REACTIONS OF FISHES TO SALTS 



273 



TABLE 9 



concentrations of NaCl when a trace of HCl is added. Also that 

 fishes in toxic concentrations of HCl live longer when NaCl is 

 present. Furthermore, NaCl is much more toxic in faintly 

 alkaline solutions than it is in faintly acid solutions. All this 

 agrees with Osterhout's conclusions as to the effect of alkalies 

 and acids on permeability. 



4. Resistance to the salts of Ca and Mg 



The only resistance experiments which have been carried on 

 with these salts are some that were performed at Chicago. The 

 experiments with Ca were performed in connection with the 

 acclimatization experiments already discussed. In brief, it was 

 found that the sun-fishes lived very well in O.OIN CaCL, while 

 the bull-heads did not live so well. Other experiments showed 

 this same relation for the nitrate and sulphate but the latter salts 

 were decidedly more toxic than the chloride and the sun-fishes 

 did not live well in solutions of them. An interesting fact was 

 noted in connection with the CaCl2 experiments. A medium 

 sized (50-gram) rock bass, after a week in O.OIN solution, showed 

 signs of degeneration of the rays of the tail fin. This degenera- 

 tion continued until nothing but the blood-reddened stub of the 

 tail was left. The other fins were not affected; the tail fin re- 

 generated when the fish was returned to tap water. 



