TABLE OF CONTENTS. 



PAOI 



Introduction 3 



Chapter I. Thb 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. Poltdacttusim 17 



A. Types of Polydactylism 17 



B. Results of Hybridization 18 



Chapter III. Stndactyusm 29 



A. Statement of Problem 29 



B. Results of Hybridization 32 



Chapter IV. RtrMPLKSSNEas 37 



Chapter V. WmoLBssNEsa 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 69 



Chapter X. Plumage 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. SilkieXBuff Cochin 76 



4. White LeghomXBlack Minorca 77 



5. White LeghomXBuff Cochin 77 



6. Black CochinXBuff Cochin *. 78 



Chapter XI. Inheritance of Elite Color, Spangling, and Barring 79 



A. Blue Color 79 



B. Spangling .80 



C. Barring 81 



1. White CochinXTosa 81 



2. White Leghorn BantamXDark Brahma 82 



3. White Leghorn BantamXBIack Cochin 82 



Chapter XII. General Discussion 86 



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 



P. Non-inheritable Characters 96 



G. The R61e of Hybridization in Evolution 97 



Literature Cited 99 



iii 



