CHAPTER III 



OUR NATURAL INHERITANCE 



1. The Three Fates.— § 2. The Elements of Our Inherit- 

 ance. — § 3. Fundamental Facts of Heredity. — § 4. 

 Recent Advances in the Study of Heredity. — § 5. Different 

 Modes of Inheritance.— § 6. Statistical Study of 

 Heredity. — § 7. Inheritance and Disease 



§ 1. The Three Fates 



AS far as biology is concerned there are three 

 determining factors in life. First and foremost 

 there is our flesh and blood relation to parents and 

 ancestors (Heredity) ; second, there are all sorts of 

 surrounding influences (EnvironrnxCnt), along with 

 which may be included opportunities ; and third, there 

 are our habits (Function), both positive and negative, 

 doing and not-doing — for sluggishness moulds the body 

 as surely as strenuous exercise. As all the three 

 factors — we may say Three Fates — are powerful and 

 always operative, it is not very urgent to argue about 

 the order of their importance. Men cannot make 

 bricks without clay — that is, the natural inheritance. 

 Neither can they make them without heat — that is, 

 the environmental factor. A living creature cannot 

 realise its initial self, i.e. its inheritance, without ac- 



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