200 THE STORY OF LIFE'S MECHANISM. 



increased power of flight would be the ones to 

 escape the lion, while the slower ones would die 

 without offspring. Thus consciousness would 

 indirectly, though not directly, result in the 

 lengthening of the legs of the animal arid in the 

 strengthening of his running muscles. Beyond 

 a doubt this factor of consciousness has been a 

 factor of no little moment in the development of 

 the higher types of organic machines. We can 

 as yet only dimly understand its action, but it 

 must hereafter be counted as one of the influences 

 in the evolution of the living machine. 



But, after all, these are only questions of the 

 method of the action of certain well demonstrated, 

 fundamental factors. Whether by natural selec- 

 tion, or by the inheritance of acquired characters 

 produced by the environment, or whether by the 

 effect of isolation of groups of individuals, the 

 machine building has always been produced in 

 the same way. A machine, either through the 

 direct influence of the environment, or as a result 

 of sexual combination of germ plasm, shows a 

 variation from its parents. This variation proves 

 of value to its possessor, who lives and transmits 

 it permanently to posterity. Thus step by step, 

 one part is added to another, until the machine 

 has grown into the intricately adapted structure 

 which we call the animal or plant. This has 

 been nature's method of building machines, all 

 based upon the three properties possessed by 

 the living cell reproduction, variation, and 

 heredity. 



