encountered. Eugenics, on the other hand, deals with the improvement of the
human race under existing conditions of law and sentiment. The Eugenist has
to take into account the religious and social beliefs and prejudices of
mankind. Other issues are involved besides the purely biological one,
though as time goes on it is coming to be more clearly recognised that the
Eugenic ideal is sharply circumscribed by the facts of heredity and
variation, and by the laws which govern the transmission of qualities in
living things. What these facts, what these laws are, in so far as we at
present know them, I have endeavoured to indicate in the following pages;
for I feel convinced that if the Eugenist is to achieve anything solid it
is upon them that he must primarily build. Little enough material, it is
true, exists at present, but that we now see to be largely a question of
time and means. Whatever be the outcome, whatever the form of the structure
which is eventually to emerge, we owe it first of all to Mendel that the
foundations can be well and truly laid.

R. C. P.

CAMBRIDGE, _March, 1911_.

* * * * *

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CONTENTS

CHAPTER I PAGE
The Problem 1

CHAPTER II
Historical 8

CHAPTER III
Mendel's Work 17

CHAPTER IV
The Presence and Absence Theory 29

CHAPTER V
Interaction of Factors 42

CHAPTER VI
Reversion 59

CHAPTER VII
Dominance 68

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CHAPTER VIII
Wild Forms and Domestic Varieties 79

CHAPTER IX
Repulsion and Coupling of Factors 88

CHAPTER X
Sex 99

CHAPTER XI
Sex (_continued_) 115

CHAPTER XII
Intermediates 125

CHAPTER XIII
Variation and Evolution 135

CHAPTER