94 



F. G. HALL. 



dioxide in the swimbladder both increased as the carbon dioxide 

 in the surrounding water increased . 



TABLE VI. 



ANALYSES OF THE SWIMBLADDER GASES OF PERCH SHOWING THE EFFECTS OF AN 

 INCREASED AMOUNT OF CARBON DIOXIDE IN THE WATER. 



The perch were placed in an aquarium when the water was at the neutral point. 

 The carbon dioxide was gradually increased and the amount recorded represents 

 the amount dissolved in the water at the time a fish was removed for analysis. 



It was observed during the preceding experiment that fishes 

 would rise in the aquarium as the carbon dioxide was increased, 

 and this suggested that the specific gravity of the fish perhaps 

 changed. It may also be seen that the oxygen percentage 

 remained fairly constant, indicating that the volume was ap- 

 parently increasing. An apparatus was devised to determine 

 if the volume of the fish did actually increase. A diagram of the 

 apparatus is shown in Fig. 2. A large bottle C of three liters 

 capacity was sealed with a rubber stopper R; a three-way 

 stopcock .S and capillary tubing connected the bottle with a 

 tambour T. The tambour controlled a marker which recorded 

 on a smoked drum D any change in volume that might take 

 place within the bottle. The bottle was immersed in a constant 

 temperature water bath B. The bottle was filled with water 

 having the same temperature as that of the constant tempera- 

 ture bath which was of the same temperature as the water in 



