THE LESSON OF HEREDITY 



color of the eyes to their child. But one may transmit 

 a tendency to black eyes, the other a tendency to blue, 

 and according as one tendency or the other proves the 

 stronger, the child will have black or blue eyes. Suppose 

 the black-eye tendency prevails for the moment that 

 is, for that individual. The blue-eye tendency is not 

 eliminated; though dormant for that generation, it 

 may reassert itself so strongly that a child of the next 

 generation will have blue eyes though both its parents 

 have black eyes. 



Nor is this all. A tendency may remain dormant, 

 and perhaps unsuspected, not merely for one but 

 sometimes for many generations, becoming at last 

 manifest again in a remote descendant. And this is 

 as true of mental and moral tendencies as of physical. 

 In short, the observed facts would seem to warrant the 

 conclusion that the organism never relinquishes any 

 tendency it has once acquired, but holds it in stock, 

 if need be, generation after generation, awaiting a 

 favorable opportunity to herald it forth. Only by such 

 a supposition can we explain the commonly-observed 

 fact of inheritance from remote ancestors, or, as Darwin 

 termed it, atavism. 



Manifestly, then, we shall greatly err if we attempt 

 sweeping estimates of a child's hereditary tendencies 

 from a study of its parents alone. Nor will it suffice 

 to turn to grandparents, or even great-grandparents. 

 Atavism assuredly reaches far back of these. But if 

 we invoke a remoter ancestry, we shall be dum- 

 founded at the response. Behold them! There were 

 eight great-grandparents; thirty-two individuals in the 



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