  PART II. DARWIN'S THEORY OF SEXUAL SELECTION. PART III. THE GENETIC AND THE OPERATIVE EVIDENCE. PART IV. SUMMARY AND CONCLUSIONS. THE GENETIC AND THE OPERATIVE EVIDENCE | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Part 1. | |
|---|---|
| PAGE. | |
| Introduction | 5 |
| Castration of Sebrights | 6 |
| A male Sebright that did not become cock-feathered after castration | 10 |
| Transitional feathers | 10 |
| Castration of F₁ hen-feathered males from Sebright by game | 11 |
| Castration of F₂ hen-feathered males | 13 |
| Hewitt’s Sebright hen that became cock-feathered in old age | 14 |
| Heredity of hen-feathering | 14 |
| Heredity of color in the cross between Sebright and Black-Breasted Game bantam | 17 |
| A. The F₁ birds | 18 |
| B. Description of F₂ birds | 19 |
| C. Back-cross of F₁ to game | 21 |
| D. The number of color factors involved | 22 |
| E. Back-cross of F₁ ♀ to Sebright ♂ | 23 |
| F. Review of the heredity of the color of the plumage in poultry | 23 |
| Endocrine cells in ovary and testes of birds | 32 |
| Luteal-cells in the testes of the male Sebright | 34 |
| Endocrine cells in the testes of mammals | 35 |
| Cyclical changes in the interstitial cells in hibernating mammals | 36 |
| Hermaphroditism in poultry and the secondary sexual characters | 37 |
| Part II. | |
| Darwin’s theory of sexual selection | 43 |
| Other theories to account for secondary sexual characters | 45 |
| Display of the male | 50 |
| Part III. | |
| The genetic and the operative evidence | 62 |
| A. Evidence from mammals | 64 |
| B. Evidence from birds | 73 |
| C. Evidence from amphibia | 86 |
| D. Evidence from crustaceans | 89 |
| E. Evidence from insects | 92 |
| Part IV. | |
| Summary and conclusions | 95 |
| Bibliography | 100 |
| Description of plates | 106 |
THE GENETIC AND THE OPERATIVE EVIDENCE RELATING
TO SECONDARY SEXUAL CHARACTERS.
———
By T. H. Morgan
———
