86 PROCEEDINGS OF THE ACADEMY OF [April, 



whose temperature in the springtime may drop almost to the freezing 

 point at night and rise in the sunlight 10° C. above the air tempera- 

 ture, it frequently passes in the space of two or three hours from an 

 arctic to a tropical environment and vice versa. In general, the 

 forms that in their natural environment have to meet sudden tem- 

 perature changes show greater powers of acclimatization than those 

 living under more constant external conditions. A comparison of 

 the powers of rapid acclimatization to high temperature of 

 Paramecium or the tadpole which lives in fresh water pools, with 

 starfish larvae which live in the ocean, shows striking differences in 

 this respect. 



Many of the terrestrial animals have developed the power of main- 

 taining a constant body temperature under widely varying external 

 conditions. This power, however, is insufficient in most cases to 

 make possible a strictly world-wide distribution. Man is able to 

 supplement natural with artificial means of temperature control. 

 Even he, however, is considerably affected by external temperatures, 

 especially high ones. One factor in producing this result appears 

 to be the effect of such temperatures on the circulation. The prac- 

 tical result of a more complete control of temperature by man would 

 be the opening up of the enormously fertile tropical regions of the 

 earth. 



The following were ordered to be printed : 



