180 



BULLETIN OF THE BUREAU OF FISHERIES 



In the work on fishes 2 or more years old the results were complicated by the 

 fact that the volume of water in relation to the size of the fish was found to be an 

 important factor in determining the temperatures survived*. Two perch were tested 

 at 30° C. in jars containing 2^ liters of water and two others in jars containing 

 about 6 liters of water. Each of the fishes in the small jars died in a little more than 

 one hour, while both of those in the large jars survived the 24-hour test in good con- 

 dition. Similar results were obtained with mature sunfishes, death at 30° C. occur- 



6 individuals -2 trials 6 indivlduals-2 trials 4 lndivlduals-2 trials 



6 individuals-2 trials 9 indivlduals-3 trials 8 indlvlduals-3 trials 



36° 



» 



6 indlviduals-2 trials 9 indlviduals-3 trials 6 individuals-2 trials 



Acclimatization 10°, 4 daya. 

 36° 38° 40° 



14 indivlduals-5 trials 6 indlviduals-2 trials 9 individuals-3 trials 



5 indlviduals-2 trials 3 lndivlduals-1 trial 3 individuals-l trial 

 Fig. 7. — Effects of high temperatures on toad tadpoles that had been acclimatized to 30° C. 

 or to 10° C. For explanation of symbols see Figures 1 and 6 



ring in from 16 to 22 hours in the small jars, while the 24-hour test period was easily 

 survived in the larger volume of water. It was found, however, that mature sun- 

 fishes could live for weeks, with infrequent change of water, in small jars at 30° C, 

 after spending the first 24 hours at that tempertature in the larger container. These 

 facts suggest that the dissolved content of the water may be of great importance as 

 a cause of death of normal individuals if the volume of water is relatively small. 



In tadpoles the results seem to indicate a definite relation between phases of 

 the life cycle and temperature tolerance. For purposes of comparison, the tadpoles, 



