308 



PHYSIOLOGY OF RESPIRATION OF FISHES 



this ability when the pH of the water was either raised above or 

 lowered below this range (Fig. 1). 



{d) The Alewife (Pomolobus pseudoharengus Wilson). — The opti- 

 mum pH for the absorption of oxygen at low oxygen tension for the 



Fig. 1. The circles represent the experimental data of the cunner {Tautogo- 

 labrus adspersus Walbaum) and the plus signs those of the mackerel (Scomber 

 scombrus L.). The abscissae give the hydrogen ion concentration; and the ordi- 

 nates the oxygen in cc. per liter at the end of the experiment. 



u 



o 

 u 



6 



Fig. 2. The circles represent the experimental data of the butter-fish {Poro- 

 notus triacanthus Peck), the plus signs those of the alewife (Pomolobus pseudo- 

 harengus Wilson) and the crosses those of the herring (Clupea harengus L.). The 

 abscissa; give the hydrogen ion concentration; and the ordinates the oxygen in 

 cc. per liter at the end of the experiment. 



alewife was about 7.3 or perhaps 7.3 to 7.6 (Fig. 2). The falling off 

 from this optimum was greatest when the hydrogen ion concentra- 

 tion was raised above this optimum. The falling off was less marked 

 when the hydrogen ion concentration was lowered. 



