Effects of Temperature on Tropical Marine Animals. 21 



in water in which it can neither move nor function. Unfortunately, how- 

 ever, no observations were made upon this interesting point ; but, crude as 

 they are, the experiments show why it is that most of these reef corals can 

 not enter the waters of the temperate regions and demonstrate that, in com- 

 mon with other marine animals, they live at temperatures within about 5° of 

 their temperature of maximum activity and within 10° of their death tem- 

 peratures. Thus the factor of safety in respect to elevation of temperature 

 is far less in tropical than in temperate marine animals, and they are, 

 relatively speaking, poorly adjusted in a physiological sense to their tem- 

 perature environment; slight differences in temperature producing a more 

 serious effect than is observed to result from similar temperature changes 

 with the marine animals of the temperate regions. Moreover, paradoxical 

 as it may seem, tropical marine animals can withstand cooling better than 

 they can survive heating above their normal life-temperature. High tem- 

 perature appears to cause death by asphyxiation, the oxygen of the sea- 

 water becoming insufficient to support the augmented metabolic activity 

 of the animal. 



