LECTURE XV. 

 THE INDIVIDUAL AND THE RACE; HEREDITY. 



§ 1. Definition of Heredity, Inheritance, Nurture, Development. 

 § 2. Heredity a Condition of Evolution. § 3. Modifications 

 and Heredity. § 4. The Organism as a Historic Being. § 5. 

 Nature and Nurture. § 6. The Other Side of Heredity. § 7. 

 Heredity and Personality. 



The water-vapour in the atmosphere condenses into rain 

 which falls on the hills; in the cold night it is changed into 

 ice, and next morning into running water again; at mid- 

 day it changes once more into water-vapour. So the same 

 material in the domain of the inorganic passes from form 

 to form, and nothing is lost. A mineral changes into some- 

 thing else and great aggregates are slowly transformed. 

 ^' They say the solid earth on which we tread in tracts of 

 fluent heat began." There is a similar sort of flux in the 

 realm of organisms, in everyday metabolism, in wear and 

 tear, in senescence. " And so from hour to hour we ripe 

 and ripe, and then from hour to hour we rot and rot, and 

 thereby hangs a tale." 



But apart from remarkable cases like Uranium liberating 

 Helium and giving origin to Radium, which liberating more 

 Helium may give origin to Lead, there is nothing in the 

 domain of things to compare with sequence of generations 

 that marks the realm of organisms. Individuals grow old 

 and die; oftener perhaps they do not grow old, but are 

 devoured; in any case they give place to others in the pro- 

 duction of which they often share. The corporeal individu- 



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