Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER in FAMILY INHERITANCE I. Physical Inheritance.?In addition to the original characteristics common to the human species and to the race to which one belongs, every individual possesses certain traits by virtue of having a certain immediate ancestry. The influence of ancestry upon a number of physical characteristics siich as eye and hair color, height, etc., has been worked out. Mental resemblances are not so definitely determined, but those which have been found, supported by the certainty of physical inheritance, lead us to expect that one’s immediate ancestry is of considerable importance in determining what his mental qualities shall be. It should not be expected that, if heredity is a real factor, two persons of the same ancestry should have original natures which are identical in every respect, except as a different environment changed them. This may be easily proved by taking physical characters which cannot be affected by environment, e. g., color of the eyes. The coefficient of correlation of two brothers in eye color is only .52, on the principle that if they were, always identical the coefficient would be 1.00 and that if there were only a chance relation between them, the correlation would be zero. To make the relation still clearer, if every person who had a brother with blue eyes had blue eyes also, and if every person who had a brother with gray eyes had gray eyes also, and so on with every color, then the coefficient would be 1.00. But if one with blue eyes might have a brother with any eye color, then the correlation would be zero. Take height as another illustration. Children of parents who are three inches above the average in height, will average only about two inches above the average, i. e., they will not be identical in height with their p…