xxviii CONTENTS 



CHAPTER XLI 

 Human Inheritance 



PAGE 



Human Traits 505 



Difficulties of Studying Human Inheritance 505 



Heritable Characters in Man 506 



Physical Characters 506 



The Inheritance of Eye-Color 507 



Brachydactyry 507 



Polydactyly and Syndactyly 509 



Skin Color 509 



Stature and Weight 511 



Color- Blindness 512 



Cretinism 513 



CHAPTER XLII 



Inheritance of Mental Traits 



(By Lewis M. Terman) 



Mental as well as Physical Traits are Heritable 514 



Amount and Nature of Variability in Intelligence 514 



Variability in Other Traits 516 



Statistical Methods Used in the Measurement of Resemblance 516 



Family Resemblance in Intelligence 517 



The Law of Filial Regression 518 



Mental Resemblance of Twins 518 



Family Resemblance not Wholly Accounted for by Environ- 

 ment 519 



The Inheritance of Genius 520 



Inheritance of Feeble-Mindedness 520 



The Kallikak Family 621 



Inheritance of Other Forms of Mental Defect 522 



En<lowmcnt of the Different Social and Occupational Classes. . . 522 



The Decreasing Fertility of Superior Stock 625 



The Importance of Eugenics 526 



The Effect of Undesirable Immigration 526 



Etigenics and Marriage 527 



The Influence of Environment and Education upon Mental Per- 



f«>rmance 528 



Heredity Sets the Limits 529 



Modifications of Mental Traits not Transmitted 529 



CHAPTER XLIII 



Man's Place in Nature 



Man the Apex of the Animal Series 631 



Man's Similarity to the Higher Animals 631 



The Fact of Progress 632 



Human Pace Unchanged 532 



Explanation of Progress 533 



