670 



Chaet I 



Graph 1 shows the reaction of a small-mouthed black bass to water containing 

 35 CO. per liter of carbon dioxide introduced at the right-hand end. The fish avoided 

 it sharply, staying very close to the left end, where the carbon dioxide was only 

 3 c.c. per liter. 



Graph 2 shows the reaction of an individual of the tadpole-cat (Scliilbeodes 

 gyrimts) to carbon dioxide of the same concentration as in the case of Graph 1. 

 It will be noted that while the fi^h was negative to the higher concentration, more 

 excursions were made into the higher concentration, and more time was spent there 

 than in the case of the small-mouthed black bass. The tadpole-cat ranks with the 

 rest of the bullhead group in having a high resistance to adverse conditions. 



Graph 3 shows the reaction of a small-mouthed black bass to 0.5 c.c. of carbon 

 monoxide per liter in the right-hand end of the gradient tank. The reaction is 

 reversed as compared with that to carbon dioxide. The avoidance of the pure water 

 is striking. 



Graph 4 shows the reaction of the black bullhead to 0.5 c.c. per liter of carbon 

 monoxide. The fish becomes slightly positive at the end of three minutes, and is 

 increasingly so as time goes on, indicating that the preference for the monoxide 

 increases with time. 



Graph 5 shows the movement of a specimen of a black bullhead when there 

 is no difference between the two ends of the tank. 



