1 82 CHARLES DARWIN 



the energy-yielding food-stuffs thus stored up the 

 animal in turn feeds and battens, reducing what was 

 before potential into actual motion, just as the steam- 

 engine reduces the latent solar energy of coal into 

 visible heat and visible movement in its furnace and its 

 machinery. How the first organism came to exist 

 biology has not yet been able fully to explain for us ; but 

 aided by chemical science it has been able to show us 

 in part how some of the simpler organic bodies may 

 have been originally built up, and it does not despair of 

 showing us in the end how the earliest organism may 

 actually have been produced from the prime elements 

 of oxygen, hydrogen, nitrogen, and carbon. Into this 

 most fundamental of biological problems, however, 

 Darwin himself, with his constitutional caution and dread 

 of speculative theorising, was not careful or curious to 

 enter. Even upon the far less abstruse and hypothetical 

 question, whether all life took its prime origin from a 

 single starting-point or from several distinct and separate 

 tribal ancestors, he hardly cared so much as to hazard 

 a passing speculation. With splendid self-restraint he 

 confined his attention almost entirely to the more 

 manageable and practical problem of the origin of 

 species by natural selection, which lay then and there 

 open for solution before him. Taking for granted the 

 existence of the original organism or group of organisms, 

 the fact of reproduction, and the tendency of such 

 reproduction to beget increase in a geometrical ratio, 

 he deduced from these elementary given factors the 

 necessary corollary of survival of the fittest, with all its 

 marvellous and far-reaching implications of adaptation 

 to the environment and specific distinctions* By doing 



