TABLE OF CONTENTS. 



PAGE 



Introduction 3 



Chapter I. The Split or Y Comb 5 



A. Interpretation of the Y Comb 5 



B. Variability of the Y Comb and Inheritance of the Variations 12 



Chapter II. Polydactylism 17 



A. Types of Polydactylism 17 



B. Results of Hybridization 18 



Chapter III. Syndactylism 29 



A. Statement of Problem 29 



B. Results of Hybridization 32 



Chapter IV. Rumplessness 37 



Chapter V. Winglessness 42 



Chapter VI. Booting 43 



A. Types of Booting 43 



B. Normal Variability 43 



C. Results of Hybridization 46 



Chapter VII. Nostril-Form 59 



Chapter VIII. Crest 67 



Chapter IX. Comb-lop r 69 



Chapter X. Plu.mage Color 71 



A. The Gametic Composition of the Various Races 71 



1. White 71 



2. Black 72 



3. Buff 72 



B. Evidence 72 



1. SilkieX Minorca (or Spanish) 72 



2. SilkieXWhite Leghorn 75 



3. SilkieX Buff Cochin 76 



4. White Leghorn X Black Minorca 77 



5. White Leghorn X Bufif Cochin 77 



6. Black Cochin X Buff Cochin 78 



Chapter XI. Inheritance op Blue Color, Spangling, and Barring 79 



A. Blue Color 79 



B. Spangling 80 



C. Barring 81 



1. White CochinXTosa 81 



2. White Leghorn Bantam X Dark Brahma 82 



3. White Leghorn Bantam X Black Cochin 82 



Chapter XII. General Dlscussion 85 



A. Relation of Heredity and Ontogeny 85 



B. Dominance and Recessiveness 88 



C. Potency 92 



D. Reversion and the Factor Hypothesis 93 



E. The Limits of Selection 94 



1. Increasing the Red in the Dark Brahma X Minorca Cross 94 



2. Production of a Buff Race by Selection 95 



F. Non-inheritable Characters 96 



G. The Role of Hybridization in Evolution 97 



Literature Cited 99 



iii 



