CHAPTER IV 



THE GEOGRAPHICAL DISTRIBUTION OF INHERIT- 

 ABLE TRAITS 



1. The Dispersion of Traits 



Traits occur in individuals and the same traits in related 

 individuals. Individuals occupy at any one moment a par- 

 ticular place. Could we take a sort of bird's eye view of the 

 continent and were each individual that bears a given trait 

 conspicuously marked, we should have a perfect picture of 

 the geographic distribution of the trait. Had we such a 

 picture for each day of the hundred thousand odd days since 

 America began to be settled and were they to pass in review 

 as in a cinematograph, then we should see the reproduction 

 and dissemination of the family trait in question. Such a 

 view would show us the traits coming across the ocean from 

 European centres, settling in a place or flitting from point 

 to point, reproducing themselves at a place and continuing to 

 increase there for generations while throwing off individuals 

 to move far athwart the face of the country and to settle 

 down as new proUferating centres. We should see two per- 

 sons with the same defect coming together as a married 

 couple and proliferating in a few years a number of new in- 

 dividuals with the same negative characters. Or we should 

 see an individual with the defect uniting with a person with- 

 out it and ending there the trail of the defect. Or, on the 

 other hand, a positive trait, like cataract, hemophilia, or 

 Huntington's chorea, would move about, settle in a spot, 



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