xiv CONTENTS 



CHAPTER PAGE 



Regulation 187 



Heteromorphosis . . . . . . .189 



Theories of Morphogenesis 190 



Preformation . 191 



Epigenesis ........ 192 



" Weismannism " 193 



Vitalism and Mechanism . . . . .194 



Summary ......... 196 



VII. VARIATION AND HEREDITY 198 



Variation 198 



The Law of Frequency of Error .... 200 



Types of Variation Curves 202 



Asymmetrical Variation .... 204 



Discontinuous Variation .... 204 



Mutations 207 



Correlated Variability 209 



Effect of Life Conditions on Variation . . .211 



Causes of Variation 212 



Heredity 214 



Heredity and Inheritance ..... 214 



Individual Heredity and Racial Heredity . . 216 



Galton's Law of Ancestral Inheritance . . 217 



Filial Regression 219 



Effect of Selection in Heredity . . . . 220 



Pure Lines 221 



Unit Characters and Mendelian Inheritance . 223 



Sex-limited Inheritance .... 233 



Economic Aspects of the Subject . 234 

 The Inheritance of Disease . . . .236 

 The Inheritance of Defects . . . .239 



Eugenics 240 



VIII. ORGANIC RESPONSE 242 



Environment ........ 243 



The Usual Conditions of Environment . . . 244 



Temperature 244 



Light .245 



Chemical Environment ..... 245 



