9. Variation in Ability 77 10. Origin of a Normal Probability Curve 78 11. The "Chance" or "Probability" Form of Distribution 79 12. Probability Curve with Increased Number of Steps 80 13. Normal Variability Curve Following Law of Chance 80 14. Cadets Arranged to Show Normal Curve of Variability 82 15. Variation in Heights of Recruits to the American Army 82 16. How Do You Clasp Your Hands? 100 17. The Effect of Orthodactyly 102 18. A Family with Orthodactyly 102 19. White Blaze in the Hair 104 20. A Family of Spotted Negroes 104 21. A Human Finger-Tip 106 22. The Limits of Hereditary Control 106 23. The Distribution of Intelligence 106 24. The Twins whose Finger-Prints are Shown in Fig. 25 108 25. Finger-Prints of Twins 110 26. A Home of the "Hickory" Family 168 27. A Chieftain of the Hickory Clan 170 28. Two Juke Homes of the Present Day 172 29. Mongolian Deficiency 174 30. Feeble-Minded Men are Capable of Much Rough Labor 192 31. Feeble-Minded at a Vineland Colony 192 32. How Beauty Aids a Girl's Chance of Marriage 215 33. Intelligent Girls are Most Likely to Marry 216 34. Years Between Graduation and Marriage 217 35. The Effect of Late Marriages 218 36. Wellesley Graduates and Non-Graduates 242 37. Birth Rate of Harvard and Yale Graduates 266 38. Families of Prominent Methodists 263 39. Examining Immigrants at Ellis Island, New York, 303 40. Line of Ascent that Carries the Family Name 331 41. The Small Value of a Famous, but Remote, Ancestor 338 42. History of 100 Babies 344 43. Adult Morality 345 44. Influence of Mother's Age 347 45. The "Mean Man" of the Old White American Stock 425 46. The Carriers of Heredity 431 INTRODUCTION