EVOLUTION AS A NATURAL PROCESS 109 



edge from the wide array of equally natural facts 

 supplied by the biologist. 



The analogies of the steamship and the locomotive 

 proved useful at many times during the discussion 

 of the fact of evolution, and even in the present con- 

 nection they will still be of service. The evolution 

 of these dead machines has been brought about by 

 man, who, as an element of their environment, has 

 been their creator as well as the director of their his- 

 torical transformations. The result of their changes 

 has been greater efficiency and better adjustment 

 or adaptation to certain requirements fixed by man 

 himself. The whole process of improvement has been 

 one, in brief, of trial and error; new inventions have 

 often been worthless, and they have been relegated to 

 the scrap-heap, while the better part has been finally 

 incorporated in the type machine. In brief, then, 

 the important elements in the evolution of these 

 examples have been three ; first, adaptation, second, 

 the origination of new parts, and third, the retention 

 of the better invention. 



Are the creatures of the Hving world so constituted 

 that biological equivalents of these three essential 

 elements of mechanical evolution can be found ? Are 

 organisms adapted to the circumstances controlling 

 their lives, and are they capable of changing naturally 

 from generation to generation, and of transmitting 

 their qualities to their ofi'spring? These are definite 

 questions that bring us face to face with the funda- 

 mental problems relating to the dynamics or workings 

 of evolution. We need not ask for or expect to find 

 complete answers, for we know that it is impossible 



