xii Contents 



2. Individual Characters 



a. Morphological Features 



b. Physiological Peculiarities 



c. Teratological and Pathological Peculiarities 



d. Psychological Characters 



II. HEREDITARY DIFFERENCES 



1. New Combinations of Characters 



2. New Characters or Mutations 



3. Mutations and Fluctuations 



4. Every Individual Unique 



r~ . '. ~~~, i 



- A i 



B. STATISTICAL STUDY OF INHERITANCE 



1. Galton's "Law of Ancestral Inheritance" 



2. Galton's "Law of Filial Regression" 



C. EXPERIMENTAL STUDY OF INHERITANCE 



I. MENDELISM 



1. Results of Crossing Individuals with one pair of contrast- 



ing characters 

 Other Mendelian Ratios 



2. Results of Crossing Individuals with more than one pair 



of contrasting characters 

 Dihybrids and Trihybrids 



3. Inheritance Formulae 



4. Presence and Absence Hypothesis 



5. Summary of Mendelian Principles 



a. The Principle of Unit Characters 



b. The Principle of Dominance 



c. The Principle of Segregation 



II. MODIFICATIONS AND EXTENSIONS OF MENDELIAN PRINCIPLES 



1. The Principle of Unit Characters and Inheritance Factors 



2. Modifications of the Principle of Dominance 



3. The Principle of Segregation 



"Blending" Inheritance 

 Maternal Inheritance 



III. MENDELIAN INHERITANCE IN MAN 



