PREFACE. Vii
one effect of the evidence here collected will be to strengthen the utmost claims I ever made for the recognition of the importance of hereditary influence.
A few of my results, and some of the evidence on which they were based, were given by me at a Friday evening lecture, February, 1874, before the Royal Institution. I have incorporated parts of that lecture into this volume, with emendations and large additions.
It had been my wish to work up the materials I possess with much minuteness ; but some months of careful labour made it clear to me that they were not sufficient to bear a more strict or elaborate treatment than I have now given to them.
The pleasant duty remains of acknowledging a debt to my friend, Mr. Herbert Spencer, for many helpful suggestions, and for his encouragement when I was planning this work ; and to reiterate my deep sense of gratitude to numerous correspondents, which I have expressed elsewhere in the following pages.
