354 DARWINISM AND THE PROBLEMS OF LIFE 



forces and conditions that impel the ball towards it are 

 not known to us. 



The Vitalists say that none of the marvellous forms 

 of the organic world can have been brought about by 

 chance, any more than the chance agencies that effected 

 the geological changes of the earth's surface could have 

 constructed a Parthenon or a steam-engine. But it has 

 been pointed out that even these structures owe their 

 origin to chance. Did James Watt go to work with the 

 idea of making a steam-engine ? Not at all. He came 

 by his first thought by chancing to observe the pressure 

 of the steam in lifting up the lid of a kettle. He then 

 confirmed his observations by assiduous experiments, 

 and so he and his successors erected machines that 

 advanced step by step, always selecting the useful and 

 rejecting the useless. The Greek style of architecture 

 arose in the same way. Natural selection acts 

 analogously. We will, therefore, regard its explanation 

 of the forms of the higher organisms as satisfactory. 



Does the purposive reaction of organisms to external 

 stimuli point to the presence of an internal vital 

 force ? 



It is suggesed that such a force, independent and 

 self-existent, must react purposively on all influences, 

 just as a magnet attracts all pieces of iron. But we 

 know that this purposive force often fails in living 

 things. An amoeba will take into its body and retain 

 for some time a particle of stone lying in its path, just 

 as it does with food. The relation of flowers and 

 insects also is often unsuitable. Many animals have 

 died out because they could not adapt themselves 



