TOLERANCE OF HIGH TEMPERATURES BY FISHES, ETC. 179 



Table 2. — Maximum temperatures, in degrees centigrade, tolerated for various lengths of time by 



normal individuals of different species 



Animal 



24-hour 

 tolerance 



4-hour 

 tolerance 



1-hour 

 tolerance 



15-minute 

 tolerance 



4-minute 

 tolerance 



Perch 



29.6 



31.5 



32.0 



32.0 



34.0 



Bass - 



32.2 



32.4 



33.4 



33.7 



36.0 +? 



Bluegill 



34.0 



34.0 



34.3 



35.7 



36.4 





34.0 



34.0 



35.3 



36.0 



36.0 +? 



Toad tadpole 



36.3 



37.3 



37.4 



38.6 



39.2 





The following features of the data contained in Table 2 and Figure 8 seem 

 worthy of mention : 



1. In each species there was a perfectly orderly progression, from the relatively 

 low temperatures that were tolerated for 24 hours to the higher temperatures, which 

 could be survived for only four minutes. 



Individuals In 2-legged stage 



36° 33° 40° 



12 individuals 18 individuals 15 Individuals 



4 trials 6 trials 5 trials 



Individuals in early 4-legged stage 



36° 38° . 40° 



9 Individuals 9 individuals 9 individuals 



3 trials 3 trials 3 trials 



Individuals In which tail was being rasorbed 



36° 38° 40° 



3 Individuals 3 individuals 3 Individuals 



1 trial 1 trial 1 trial 



Fio. 6. — Effects of high temperatures on "normal" toad tadpoles in various stages of develop- 

 ment. The symbols are the same as in Figure 1, except that the black sectors include indi- 

 viduals in heat rigor as well as those actually dead 



2. For every time period, with one minor exception, the relative degrees of heat 

 tolerated by the five species of animals fell in the same sequence — -that is, the ascend- 

 ing order of tolerance was (a) perch, (&) bass, (c) bluegill, (d) sunfish, (e) toad tadpoles. 



A few tests were made in the endeavor to determine the relation of age to toler- 

 ance of high temperatures. Perch 6 months old showed about the same resistance 

 as those 18 months old, usually tolerating 30° C. (86° F.) but not 32° C. (89.6° F.). 



