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chromosome seat and a blue-eye determiner in the other may 
have when married both brown-eyed and blue-eyed children, and 
these will occur in proportions approximating three with brown 
eyes to one with blue eyes. Thus you see in people the same 
kind of results you see in peas, because the same law governs the 
inheritance in both. 
When people pure for brown-eye marry blue-eyed people, only 
brown-eyed children are born, though the children often are blue- 
eyed for the first few months. In some cases the brown pigment 
may be very late in developing, perhaps several years after birth. 
Brown-eyed children of such unions, if they should marry their 
own type, could have both brown- and blue-eyed children. But, if 
they had only one child, the chances are three to one that it 
would be brown-eyed. Nevertheless it might be blue-eyed, al- 
though a brown-eyed child is three times more likely to be born. 
Brown- and white-eye in peas, and brown- and blue-eye in 
people are only illustrations of many thousands of pairs of char- 
acters and character-determiners in peas and people. As a 
student of inheritance views a pea or a person, each is a great 
collection of pairs of hereditary character-determiners which, 
under the appropriate environment, give rise to various kinds of 
characteristics, each according to its kind. Different environ- 
ments may affect them differently either for better or for worse, 
causing “ good” or “bad” traits to appear. 
Environment and heredity are not quarrelsome forces, as many 
laymen seem to think. A person, like a pea, cannot help its 
heredity. Once born, that is settled. But an intelligent person 
can alter or modify many of his characters by looking after his 
environment. Some characters are but slightly changed, others 
very much so, by ordinary differences in environment, such as 
variations in climate. Which characters are which is still a field 
for much study, although some of each kind are well known. 
For the most part, the effects of various environments on the ex- 
pressions of different character-determiners are unknown. This 
field is still a wilderness. But explorers are more and more 
penetrating it. Many paths have been started through it since 
1900, when the study of inheritance as a science was born. 
Probably all people are hybrids in regard to some of their 
