TOLERANCE OF HIGH TEMPERATURES BY FISHES, ETC. 



175 



group. During the test periods, especially during the early hours, observations 

 usually were made exactly on schedule times, or within a very few minutes of them. 



In acclimatization at 30° specimens were discarded if the temperature was 

 found to have risen above 31°. The work of Loeb and Wasteneys (1912) had 

 shown that exposure for a short time to a high temperature produced lasting results, 

 and, as will be seen later, experiments in this series bore out their conculsion; so it 

 was felt that an exposure to a temperature of 31° for even a short time was enough 



Acclimatisation 30° C. for 1 day. 



_36_o 38° 



8 Individuals, 5 trials 

 36° 



Acclimatization 30° C. for 4 days. 



38° 



6 individuals, 3 trials 

 40° 



HI 



5 individuals, 3 trials 7 individuals, 4 trials 4 individuals, 3 trls. 

 30° 



Acclimatization 10° C. for 1 day. 

 322 



2 individuals, 1 trial 12 individuals,? trials 6 individuals, 2 trls. 



Acclimatization 10° C. for 4 days. 

 30° 32° 34° 



5 individuals, 3 trials 6 individuals, 6 trials. 5 individuals. 5 trls 

 Acclimatization 10° C. for 16 days. 



8 individuals, 5- trials. 



Fig. 2. — Effects of high temperatures on large-mouthed black bass that had been acclimatized 

 to 30° C. or 10° C. For explanation of symbols see Figure 1 



to invalidate the experiment. During the test periods any fluctuations of tempera- 

 ture, either upward or downward, were important. The normal variations were 

 0.2° to 0.3° C. They seldom were more than this, except when the apparatus was 

 seriously out of order, and if at any time in a test the temperature was found to be 

 as much as 1° above or below that specified the results were discarded. This rule 

 was very important, because it was found that a drop of 1° or 2° for a short time 

 during the early hours of a test apparently enabled a fish to become adjusted and to 

 68618—28 2 



