INHERITANCE 183 



Since pure -bred animals are now usually reared under 

 similar conditions (those of the North being protected 

 from the vicissitudes of climate quite as much as those 

 of the South), we may study pure -bred animals from 

 the Darwinian standpoint, and expect that the inheri- 

 tance of every long and well-established characteristic 

 will be the rule and non-inheritance the exception. 

 Without criticizing any of the breeds, it may be said 

 that some of their characteristics have not been well 

 established, because they have been acquired in the last 

 few generations. The subject of inheritance of farm 

 animals is difficult and complex, since all breeds of 

 domestic animals may be said to be "made-up breeds"; 

 for, in the stricter sense of the word, we have no pure- 

 bred animals. But this does not concern us here and 

 now. Under certain rules and regulations, we have 

 agreed to call certain varieties of horses thoroughbred, 

 pure -bred, or full -blood; but their pedigrees need not 

 be traced back very far before they end in unknown or 

 mixed -blooded ancestry. 



A plausible but misleading theory of inheritance 

 has been formulated as follows: The offspring receives 

 one-half of its inheritance from its parents, that is, 

 one -fourth from its :nale and one -fourth from its female 

 parent; one -fourth from its four grandparents, one- 

 eighth from its eight great -grandparents, and so on. 

 Mathematically expressed, the inheritance would be 

 as follows: 



GENERATIONS 



First Second 'bird Fourth Fifth Total 



