86 



F. G. HALL. 



TABLE II. 



THE RESULTS OF ANALYSES OF THE SWIMBLADDER GASES OF VARIOUS SPECIES OF 

 FISHES SEINED IN UNIVERSITY BAY, LAKE MENDOTA, NEAR THE SURFACE, 



SEPTEMBER 12-14, 1921. 



The dissolved gases ranged as follows: Oxygen = 3.8-4.0 c.c. per liter; Carbon 

 dioxide = 1.7-2.0 c.c. per liter. The temperature was 22.2 C. 



At different times during the year, fishes were taken from 

 tanks in the laboratory and the gas content of their swimbladder 

 analyzed for the purpose of controls for various experiments. 

 The tanks were supplied with water pumped from Lake Mendota. 

 The water was well aerated before it was introduced into the 

 tanks, because that coming directly from the pipes was super- 

 saturated with atmospheric gases. The fishes were kept for 

 long periods of time in these tanks in apparently good condition, 

 although for most of the experiments fishes were used that had 

 been brought in from the lake within a period of from 10 to 14 

 days. The results of the analyses of apparently normal fishes 

 taken from laboratory tanks are summarized in Table III. 



It is shown that the normal compositions of gases in the 

 swimbladder of perch was 19.9 per cent, oxygen and 0.63 per cent, 

 carbon dioxide when the fishes were kept in a normal environ- 

 ment. 



