244 . Heredity. 



rence to type and the principle of adaptation to con- 

 ditions. 7 



That like produces like is universally but never abso- 

 lutely true. The offspring resembles its parents in all 

 fundamental characteristics. The human child, for in- 

 stance, resembles its parents in the possession of all the 

 characteristics which distinguish living things from 

 those which are not alive, as well as those which distin- 

 guish animals from plants. The chemical, physical, 

 and physiological changes which take place in its body 

 and the histological structure of its tissues are like those 

 of its parents, and its various organs are the same in 

 form and function. All the characteristics which unite 

 it with the other vertebrates, as a member of the sub- 

 kingdom Vertebrata, are like those of its parents, and 

 also those which place it in the class Mammalia, and in 

 its proper order, family, genus, and species. It also 

 shares with its parents the features or race characteris- 

 tics of the particular tribe or race to which they belong. 

 If they are Chinese, Indians, or negroes, the child be- 

 longs to the same race, and manifests all the slight, 

 superficial peculiarities of form, constitution, and char- 

 acter by which that race is distinguished. Even the in- 

 dividual peculiarities of the parents, intellectual and 

 moral as well as physical, are now known to be heredi- 

 tary. Since this holds true of any other animal or plant, 

 we must recognize the universality of the law of hered- 

 ity, but we must not overlook the equally well-estab- 

 lished fact that each organism is the resultant of this 

 law and another, the law of variation. The child is like 

 its parents, but not exactly like them. It is not even a 

 compound of characteristics found in one or the other 

 of them, but has individual peculiarities of its own; 

 slight variations which may not have existed in either 



