CHAPTER III 

 ACQUIRED CHARACTERS 



THE simplest and most obvious theory of 

 heredity is that of growth through use and of 

 organic change through the accumulated effects 

 of use. It is plain that activity causes organs 

 to grow. The laborer acquires additional 

 strength by using his arms or his hands to do 

 a particular sort of work. Those who walk 

 regularly find that they can go farther than 

 before the regular exercise began. Blacksmiths 

 have strong arms, musicians have dexterous 

 fingers, and porters have strong legs and 

 backs. It is not necessary to give extended 

 examples of what every one knows. Even the 

 crudest observations verify the law that use pre- 

 cedes and is the cause of growth and change. 



Differences of opinion, however, arise when 

 it is asserted that these organs, developed 

 through use, are inherited by descendants in 

 their improved form. There can, of course, 



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