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 



VIH. ORGANIC RESPONSE 242 



Environment 243 



The Usual Conditions of Environment . . 244 



Temperature 244 



Light .245 



Chemical Environment 245 



