94, BIOLOGY AND SOCIAL PROBLEMS 



modified in that it may be gradually moved, by 

 selection, for instance, in one direction or an- 

 other. Marvelously stable as the unit charac- 

 ters are, they are not in their stability com- 

 parable with the chemical elements, for they 

 exhibit gradual changes. Whether these 

 changes are to be accounted for on the basis 

 of inherited modifiers, a kind of additional 

 demon behind the demon unit character, or 

 by some other process, is a question for the 

 future to decide. Of one point we can feel 

 fairly certain, unit characters are modifiable. 

 Although these results have been worked 

 out almost exclusively on the smaller, rapidly 

 breeding animals, there is no reason to sup- 

 pose that they do not apply with full force 

 to the human being. Already a long list of 

 characteristics, which are inherited in man in 

 accordance with one form or another of the 

 Mendelian principles, is known. This list in- 

 cludes certain eye colors ; certain hair colors 

 and hair forms, such as straight, wavy, and 

 curly ; certain skin colors, such as that of the 

 blond and the brunette ; pale, fresh, and col- 

 ored complexions in the white race ; stature, 

 form of head, and nose in certain races ; mu- 

 sical and non-musical temperaments ; various 



