l basis for the
following characteristics: to live past maturity, to reproduce
adequately, to live happily and to make contributions to the
productivity, happiness, and progress of society. It is desirable to
discriminate as much as possible between the possession of the germinal
basis and the observed achievement, since the latter consists of the
former plus or minus environmental influence. But where the amount of
modification is too obscure to be detected, it is advantageous to take
the demonstrated achievement as a tentative measure of the germinal
basis. The problem of eugenics is to make such legal, social and
economic adjustments that (1) a larger proportion of superior persons
will have children than at present, (2) that the average number of
offspring of each superior person will be greater than at present, (3)
that the most inferior persons will have no children, and finally that
(4) other inferior persons will have fewer children than now. The
science of eugenics is still young and much of its program must be
tentative and subject to the test of actual experiment. It is more
important that the student acquire the habit of looking at society from
a biological as well as a sociological point of view, than that he put
his faith in the efficacy of any particular mode of procedure.

The essential points of our eugenics program were laid down by Professor
Johnson in an article entitled "Human Evolution and its Control" in the
_Popular Science Monthly_ for January, 1910. Considerable parts of the
material in the present book have appeared in the _Journal of Heredity_.
Helpful suggestions and criticism have been received from several
friends, in particular Sewall Wright and O. E. Baker of the United States
Department of Agriculture.
PAUL POPENOE.

WASHINGTON, _June, 1918._

TABLE OF CONTENTS

PAGE

PREFACE v

INTRODUCTION BY EDWARD A. ROSS xi

CHAPTER

I. NATURE OR NURTURE? 1

II. MODIFICATION OF THE GERM-PLASM 25

III. DIFFERENCES AMONG MEN 75

IV. THE INHERITANCE OF MENTAL CAPACITIES 84

V. THE LAWS OF HEREDITY