CHAPTER I. 



HEREDITY. 



HEREDITY is that mysterious influence which fore- 

 ordains that the offspring shall be in the likeness of its 

 parents. It is one of Nature's great fundamental laws, 

 and it is universal. In the meanest forms of animal 

 and vegetable life, as in the highest, each family must 

 produce its like. Grapes are not gathered from thorns, 

 nor figs from thistles. All through Nature, from the 

 amoeba to man, from the yeast-plant to the oak, every 

 kind produces after his kind. Yet plants and animals 

 are not tied down by this law to endless sameness. 

 Certainly Nature will not permit any rude violation 

 of this law of hereditary transmission, but, where the 

 change is sufficiently gradual, where it is, so to speak, 

 the work of Nature herself, it is with the aid of this 

 very law that modifications are built up, the changes 

 brought about in the individual by the action of the 

 environment being repeated and perpetuated in the 

 offspring by the action of the laws of heredity. These 

 modifications sometimes tend toward the elevation of 

 the family type evolution, and sometimes toward its 

 ex tinction dissolution. 



