CONTROL OF HEREDITY. 



CHAPTER I. 

 INHERITANCE, VARIATION AND SELECTION. 



If two acorns be planted they will sprout into plants which wilt 

 in due time grow to be two oak trees. The manner of growth in 

 both will be the same. Each will increase its diameter by adding 

 external layers of wood; each will have its trunk knotted and 

 gnarled in the manner peculiar to oak trees ; and from the trunk of 

 each will grow branches having like characteristics. From the 

 trunks and branches will grow crooked and twisted twigs which 

 will bear those distinctively shaped leaves known as oak leaves 

 and other acorns like those from which the tree originally came. 



PECULIAR DIFFERENCES IN TREES. 



While each of these trees is unmistakably an oak, the two will 

 differ from each other in many particulars. One will lean to the 

 right, the other to the left. Where one tree will have a single 

 large branch growing from the trunk and smaller branches spaced 

 irregularly about or above it, the other will have two or more 

 medium-sized branches with smaller branches differently spaced 

 and of different diameters. In fact, if the two trees be accurately 

 compared with each other it will be found that they are not exactly 

 alike in any particular, and this will be true whether the two origi- 

 nal acorns came from the same tree or from different trees of the 

 same species. Yet in spite of these differences there will not be 



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