CONTENTS 



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 Men- 

 delian Principles 



1. The Principle of Unit Characters and 

 Inheritance Factors 



Inheritance Factors and Germinal 

 Units 



2. Modifications of the Principle of Domi- 

 nance 



Sex and Sex Limited Inheritance 

 Sex Linked Inheritance 



3. The Principle of Segregation 

 "Blending" Inheritance 



III. Mendelian Inheritance in Man 



CHAPTER IV. INFLUENCE OF ENVIRONMENT 



A. RELATIVE IMPORTANCE OF HEREDITY 

 AND ENVIRONMENT 



L Former Emphasis on Environment 



2. Present Emphasis on Heredity 



3. Both Indispensable to Development 



