CHAPTER II 



THE BIOLOGICAL CONTROL OF LIFE 



§ 1. The Idea of Evolution.— § 2. The Idea of Controlling Life.— 

 § 3. Illustrations of the Control of Life. — § 4. Faith in 

 Science. 



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§ 1. The Idea of Evolution 



NE of the biggest intellectual legacies from the 

 nineteenth century was the theory of Organic 

 Evolution. By this is meant not only the general idea 

 that the present is the child of the past and the parent of 

 the future, but the conviction that the plants and animals 

 of to-day have arisen from an antecedent realm of plants 

 and animals of (on the whole) rather simpler type, and 

 that the change has been brought about by a co-opera- 

 tion of definite natural processes, such as varying and 

 sifting, comparable to processes which can be seen going 

 on to-day. The realm of organisms has had a history, 

 but, more than that, a natural history which is in its 

 essential features still continuing and therefore observ- 

 able. It is true, indeed, that we do not as yet know 

 much about the causes of varying among living creatures, 

 but we are sure that variations crop up frequently in 



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