CONTENTS PAGE I.--THE SOURCES AND AIMS OF THE SCIENCE OF EUGENICS 3 II.--THE BIOLOGICAL FOUNDATIONS OF EUGENICS 49 III.--HUMAN HEREDITY AND THE EUGENIC PROGRAM 133 LIST OF ILLUSTRATIONS FIG. PAGE 1.--Increase of population in the United States and the principal countries of Europe from 1800 to 1900 26 2.--Relative and absolute numbers of prisoners in the United States from 1850 to 1904 30 3.--Recorded measurements of the stature of 1052 mothers 57 4.--Model to illustrate the law of probability or "chance" 59 5.--Plinth to illustrate the difference between variability (fluctuation) and variation (mutation) 64 6.--Curves illustrating the relation between the pure line and the species or other large group 67 7.--Diagram showing the course of color heredity in the Andalusian fowl 83 8.--Diagram showing the course of color heredity in the guinea-pig 85 9.--Diagram illustrating the relation of the germ cells in a simple case of Mendelian heredity 92 10.--Diagram illustrating the phenomenon of regression 107 11.--Diagrams showing the relation between order of birth and incidence of pathological defect 125 12.--Coefficients of heredity of physical and psychical characters in school children 144 13.--Family history showing brachydactylism. Farabee's data 151 14.--Family history showing polydactylism 155 15.--Mother and daughters showing "split hand" _Facing_ 156 16.--Two family histories showing "split foot" _Facing_ 158 17.--Family history showing congenital cataract 159 18.--Family history showing a form of night blindness 161 19.--Family history showing a form of night blindness 163 20.--Family history showing Huntington's chorea 165 21.--Family history showing deaf-mutism 167 22.--Family history showing feeble-mindedness 169 23.--Family history showing angio-neurotic oedema 170 24.--Family history showing tuberculosis 171 25.--Family history showing infertility 175 26.--Family history showing ability 177 27.--Family history showing ability 179 28.--History of three markedly able families 183 29.--History of _Die Familie Zero_ 185