CHAPTER II 

 HEREDITY: ITS MEANING AND INFLUENCE 



The word heredity has long been used by scientific men 

 when discussing the important subject of breeding animals 

 and plants. As commonly defined, it means the reproduc- 

 tion in the offspring of the characteristics of the parents. It 

 means more than that, however, because the parentage of 

 an animal or plant extends further back than one generation. 



The degree or extent that characteristics may be inherited 

 from parents, grandparents, and more distant generations, 

 can not be absolutely determined. Yet, that animals and 

 plants do inherit from other generations than the parents, is 

 a matter of common knowledge. In fact, everything found 

 in the animal, whether physical or mental, excepting cer- 

 tain diseases, has been transmitted through previous genera- 

 tions. We know that under average conditions there is a 

 certain degree of resemblance between an animal and its 

 various ancestors. Yet there are conditions which greatly 

 affect heredity. Writing on "the complex nature of hered- 

 ity," Davenport says:* "The most disconcerting principle 

 in all improvement operations lies back of the obvious fact 

 that the offspring is not like the parent. Having two parents, 

 he could not of course be like them both. The fact is, how- 

 ever, that for the most part he is not like either one of them, 

 nor yet is he like the two combined. The most that can be 

 said is that the offspring resembles his parents, and that all 

 his characters are to be found somewhere in his parentage." 



The persistence of heredity is a most important factor 

 in its influence on the offspring. The older and better 

 established the family, the more uniform and certain is the 

 transmission. We say that an animal, family, breed, or 



*Domesticated Animals and Plants, 1910, p. 154. 



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