REACTIONS OF FISHES TO SALTS 265 



normal rock bass are negative to low oxygen (1 cc. per liter at 

 the low end) as has been shown also by Shelf ord and Allee ('13, 

 p. 236). Large rock bass seem to be an exception to this general 

 rule as they are not always negative to low oxygen, and in some 

 cases seem to definitely prefer the low oxygen end of the gradient, 

 spending a majority of the time there. The cause of this re- 

 action has not been determined but it may have to do with the 

 concentration of hydrogen ion which would probably be a little 

 higher in the low oxygen end than in the high oxygen water, the 

 difference being due to the difference in the effect of the two 

 kinds of water upon the elimination of carbon dioxide by the 

 organism. 



Fishes Nos. 6 to 8 (table 5) are the individuals occurring under 

 the same numbers in table 4. There it was noted that their reac- 

 tion to the CaCl2 had become more positive than the normal re- 

 action and in table 5 it will be noted that these fishes are less sen- 

 sitive to the low oxygen also. Fish No. 5 is also the same in tables 

 4 and 5 and it will be noted that this fish was positive to both 

 low oxygen and 0.01 N CaCL. Experiments in low oxygen gra- 

 dients were not performed with these fishes later in their period 

 of starvation but the data given indicate that as they become 

 somewhat starved they at the same time become less negative 

 to low oxygen. This indicates that their metabolic rate is slower 

 than normal. 



D. ACCLIMATIZATION AND THE REACTION OF FISHES 



During the course of the experiments, considerable evidence 

 was accumulated concerning the effect of acclimatization upon 

 the reactions of the fishes. A few experiments with fishes in 

 CO2 gradients indicated that these fishes after living for two to 

 three weeks in water whose CO2 concentration was 8 to 10 cc. 

 per liter, were more sensitive to the CO2 than normal fishes. To 

 determine whether or not the presence of an excess of salt would 

 result in similar reactions to the salt in a gradient, a series of 

 acclimatization experiments with CaCl2 was run. 



A medium-sized (45-gram) rock bass was graphed in a CaCl2 

 gradient; its normal reaction was decidedly negative to O.OIN 



