CHAPTER X 

 VARIATION 



No biological fact is more clearly recognized than the 

 tendency of all plants and animals to vary. In a broad 

 way, individuals resemble their parents. Through hered- 

 ity the qualities of the parent are transmitted to the off- 

 spring. A horse begets other horses and not pigs. We 

 do not gather grapes of thorns nor figs from thistles. 

 Thus has come about the old adage " like begets like," 

 but this aphorism applies only within certain limits and 

 fails to take into account the inexorable law of variation 

 by which the offspring is never exactly like the parent. 

 It is true that the offspring of a horse will always be a 

 horse and not a cow. It is even true that the progeny of 

 a trotting horse will be a trotting horse, but the keen 

 judge of horses is able to discern slight variations in form, 

 color, disposition or ability to perform. 



No two animals are exactly alike. The difference 

 may be slight or very marked. From the same sire and 

 dam, the offspring may differ widely in character among 

 themselves. In a large family of boys, the physical 

 characters and mental dispositions of the individual 

 members of the family may be very different. It has 

 happened in the history of trotting and running horses 

 that own brothers have varied widely in their ability 

 to win in speed competitions. 



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