383 Eelation op Water to the Behavior of 



limiting factor in an arid region and the prime essential for metabolism, the 

 behavior of the potato beetle in a desert is determined chiefly by the water- 

 content of its environment. Henderson (1913) states: 



" Water, of its very nature, as it occurs automatically in the process of cosmic 

 evolution, is fit, vs'ith a fitness no less marvelous and varied than that fitness of 

 the organism which has been won by the process of adaptation in the course of 

 organic evolution. ... In truth, Darwinian fitness is a perfectly reciprocal 

 relationship. In the world of modern science a fit organism inhabits a fit 

 environment." 



These results upon the potato beetle indicate that its marvelous fitness and 

 adaptation to water is such a " reciprocal relationship." 



The experiments were performed at the Desert Laboratory of the Carnegie 

 Institution of Washington, and it is a pleasure to acknowledge my indebtedness 

 to its director, Dr. D. T. MacDougal, for his interest manifested. I must also 

 acknowledge my great indebtedness to Professor W. L. Tower, of the University 

 of Chicago, who made it possible for me to continue this problem at Tucson. 

 The following bibliography gives only the literature cited. 



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