REACTIONS OF FISHES TO SALTS 



259 



Fig. 2 Showing the reaction of bull-heads (Ameiurus melas) to Ca(No3)2, 

 alone, and in combination with a trace of NaNOs. The concentration of the 

 calcum salt was 0.01 N throughout and that of the sodium salt 0.0002 N; experi- 

 ments performed in distilled water; numbers at left indicate time in minutes. 



centrations of the two salts are reversed, i.e., when the calcium 

 nitrate is present in O.OIN concentration and the sodium as a 

 trace (0.0002N). The data for table 2 were obtained from 

 graph experiments and also from readings. The same fishes were 

 used in the gradient with the different conditions, i.e., they 

 were first graphed in the gradient with the sodium salt (e.g.) 

 alone and then again after the calcium salt had been added to 

 the flow. To illustrate more accurately this method of experi- 

 ment figure 2 is inserted. The graphs shown in this figure are 

 3 of those made by 4 bull-heads. The experiments were run 

 as follows: The gradient with only Ca(N03)2 flowing in at the 

 salt end, was obtained by allowing the flow to continue for 30 



TUB JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 19, NO. 3 



