250 



VICTOR E. SHELFOED AND W. C. ALLEE 



TABLE 15 



Showing the reactions of fishes to boiled water with oxygen added to balance the oxygen 

 of the tap. The gradient consisted of a few parts per million of calcium, el cetera, 

 15 cc. of nitrogen, 2 cc. of free and 1 cc. of half-bound carbon dioxide. Data 

 arranged as in the preceding tables. Controls were gradients between tap and boiled 

 water ivith no oxygen added, so that they are like the experiments tabulated in 

 table 11, p. 243. 



1 Fish stayed in boiled water plus oxygen. After finding the tap water they 

 spent most of the time in that end. 



- Fish did not encounter tap water until the end of the first five minutes. After 

 the tap water was encountered the fish spent 62 per cent of the time in that end. 



^ Fishes driven asymmetrically. 



^ No evidence of a reaction. 



c. Boiled water and carbon dioxide 



The results of these experiments are shown in table 16. The 

 oxygen content of the boiled water was less than 1 cc. per liter 

 as it flowed into the tank. The carbon dioxide content was kept 

 as nearly as possible at 50 cc, per liter at the boiled water and 

 3 cc. per liter at the tap water end. As shown by the table and 

 by the graphs, chart 4, the reactions of all the fishes were very 

 decided. In every case they showed a strong time preference 

 for the tap water and turned back from the treated water much 

 oftener than from the tap. All the testing (backing-starting) 



