230 



VICTOR E. SHELFORD AND ^Y. C. ALLEE 



a. Reaction to carbon dioxide 



The reactions of fishes to carbon dioxide in water are shown 

 in table 6, with ilhistrative graphs in chart 1. The experiments 

 fall into the following three classes: (a) Those with a difference 

 of 5 to 10 cc. between the two ends; in these experiments the 

 principal gradient was in the two center divisions as shown for 

 oxygen in figure 2, page 227. (b) Those with a difference of 

 about 19 cc; in taking the readings of these, four central divi- 

 sions were regarded as constituting the principal gradient, (c) 



TABLE 6 

 Showing the reactions of fishes to a gradient of carbon dioxide in lap water. The 

 experiments bearing numbers only, were performed with fishes taken directly from 

 the stock aquaria, while the experiments bearing numbers and the letter A were 

 peiformed tvith the same fishes, control and experimental individuals being inter- 

 changed. The control fishes of the first period of observation, after having become 

 accustomed to going back and forth in the uniform tank were exposed to the gradient, 

 while fishes accustomed to meeting the gradient were put into a tank where no 

 gradient existed. For description of the apparatus, et cetera, see pp. 225-229; cor- 

 responding ends of the controls are designated by the same letters. H indicates 

 high carbon dioxide and L low carbon dioxide. 



EXPT. 

 NO. 



85 

 87 



87 X 

 86 X 

 86 

 46 



46 A 

 44 

 45 



45 A 

 47 



47 A 

 48 



48 A 

 49 



49 A 

 52 



52 A 

 53 



53 A 



Abramis 



Ambloplites. . 

 Mioropterous. 



Hybopsis 



No.ropis 



Hybopsis 



Hybopsis 



Ambloplites.. 



Abramis 



.\bramis 



Lepomls 



Lepomls 



Amelurus 



Ameiurua 



Umbra 



Umbra 



Catostomus.. 

 Catostomus.. 



Notropis 



Notropis 



Totals... 

 Average. 



CO2 



IN CC. 



PER 

 LITER 



2 

 2 

 2 

 2 



2.5 



2.5 



7. 



7 



7 

 12 

 12 

 12 

 12 

 12 

 12 

 15 

 15 



6 



6 



150 



7.5 



7 



7 



7 

 7-13 

 7-1: 

 21 

 21 

 72 

 72 

 72 



1081 

 54 



CROSS- 

 ED CEN- 

 TER 



TOTAL 



TIME 

 IN MIN. 



15 

 15 



15 

 9.5 

 9.5 



30 



30 



30 



30 



30 



30 



30 



30 



30 



30 



30 



30 



30 



20 



20 



494 

 24 



PER CENT OF 



TIME IN HALVES 



OF TANK 



Expt. 



H L 



1584 

 79 



Control 



H L 



871 



TURNED BACK 



IN GRADIENT 



FROM HIGH (H) 



OR LOW (L) 



Expt. 



H L 



TEMP. 

 DEG. C. 



Control 



H L 



