Tem-perature: Metabolic Aspects and Perception 



347 



als alter their temperature resistance within genetic limitations. There are 

 numerous examples of acclimatization to heat and to cold which may have a 

 genetic basis. A frequently-cited but never-repeated experiment was conducted 

 by Dallinger,^^ in which by very gradual increases in temperature flagellate 

 Protozoa were after seven years made to survive and reproduce at temperatures 

 as high as 70° C, well above the temperature which was lethal at the begin- 

 ning of the experiment. In hot springs chlorophyll-bearing algae are common 

 at 60° C, and some non-green algae at 70°.-^ Rhizopods are reported from 



A cc/fm at/on 



ternpercf/ure 



■^O 'C. 



Fig. 86. Relation between acclimatization temperature and the temperature lethal for 

 50 per cent of goldfish in 14 hours. Arrows indicate death of ail of a group of fish. From 

 Fry, Brett, and Clawson.^*" 



natural waters at 54.5°, flagellates at 51°, and ciliates at 46°. Brues found 

 numerous insects and some crustaceans and snails in hot springs at around 38°; 

 Chironomus larvae were thriving at 49-51° C. Fish rarely are found at tem- 

 peratures above 30°, but frog tadpoles have been collected from water at 40- 

 4jo_27 y^ese natural temperatures are well above lethal temperatures deter- 

 mined on laboratory specimens reared at lower temperatures. 



Mayer^-" reports Aurelia from Halifax dying at 29-30°, those from Tor- 

 tugas at 38.5°; also Limulus from Woods Hole dying at 41.0°, and those from 

 southern Florida at 46.2°. Mayfly nymphs from a 11.6° stream died at 22.4°, 

 whereas others of the same species from a 14.5° habitat died at 24.7°.^"^ 

 Specimens of the prawn Pandalus from waters 5° to 7° C. at Kristineberg, 

 Sweden, could not be maintained in aquaria at temperatures above 11° C, 



