REACTIONS OF FISHES TO ATMOSPHERIC GASES 



247 



In the closely observed experiments, Abramis, Hybopsis and 

 Notropis may be said to have reacted with considerable pre- 

 cision, either by rising to the surface or by spending more of the 

 time in the high end or by turning back definitely from the 

 center. In the long experiments, the amount of rising to the 

 surface was not definitely noted in all cases although this reac- 

 tion may dominate over all others. Ameiurus and Catostomus 

 sometimes give this reaction so the preference of these fishes 

 for the boiled water as shown in table 12 is open to some 

 question. 



2. Low oxygen stock. The low oxygen stock consisted of a 

 number of Abramis, Ameiurus and Umbra. They were put in 

 a small glass-sided aquarium and supplied with water from the 

 boiling-^pparatus, which water was changed every few days and 

 which always showed an oxygen content of less than 1 cc. per 

 liter. The carbon dioxide at times was as high as 8 cc. per liter. 

 Tables 13 and 14 give the results of experiments upon this stock 



TABLE 13 



Showing the reactions of fishes from the low oxygen stock to a boiled water gradient. 

 The data are arranged as in the preceding tables; compare with table 11. Controls in 

 tap; gradient between tap (T) and boiled (B); corresponding ends of the control 

 designated by the same letters. Tap water contained 8 cc. per liter. Boiled less 

 than 1 cc. per liter. 



^ Fish same as 24, left in tank one hour and forty minutes, and read again. 

 ^ Control reading incomplpte. 

 ^ Three fishes in control. 



