FIGS. 2A, 2B. Upper row, to right, “Transitional” hackle feathers (2A), and a slightly later changed-over feather from wing-bow (2A), and from back (2B). Second row, to left, old (2), transitional (2_a_), and changed-over feather (2_b_), from saddle of Sebright. FIG. 3. Three feathers (tail-covert, wing-bow, and saddle) of an F₂ hen-feathered game-like male. FIG. 4. A series of breast feathers from an F₂ bird. At one end of the series (the left) the feather is spangled, at the other barred. FIG. 5. A series of breast feathers from another F₂ bird. At one end of the series (the left) the feathers are penciled, at the other end they are barred. [Illustration: T. H. MORGAN PLATE 1 JULIUS BIEN, N.Y. 1. Black Breasted Game Bantam male. 2. Female. 3. Sebright male. 4. Castrated Sebright male. ] [Illustration: T. H. MORGAN PLATE 2 JULIUS BIEN, N.Y. 1. Hen-feathered F₁ male. 2. F₁ female. 3. Castrated F₂ male. 4. Castrated F₁ male (Fig. 1). ] [Illustration: T. H. MORGAN PLATE 3 JULIUS BIEN, N.Y. 1. Castrated Sebright male. 2. F₂ Hen-feathered male. 3. Same castrated. 4. F₂ Castrated male. ] [Illustration: MORGAN PLATE 4 1. Black-Breasted Game male. 2. Black-Breasted Game female. 3. Sebright male. 4. Sebright female. 5. Hybrid male. 6. Hybrid female. ] [Illustration: MORGAN PLATE 5 1. Adult Sebright male. 2. Castrated Sebright male. 3. Castrated F₁ male. 4. Another castrated Sebright male. 5. Castrated Sebright male with testes regenerating. 6. Same as 5 after second removal of testes. ] [Illustration: T. H. MORGAN PLATE 6 JULIUS BIEN, N.Y. Feathers of “light” colored Sebright (1, 2) that changed to cock-feathers after castration (1ªa, 2ª).] [Illustration: T. H. MORGAN PLATE 7 JULIUS BIEN, N.Y. Feathers of F₁ hen-feathered male before (1), and after (1ª) castration. Feathers of a darker hen-feathered male before (2), and after (2ª) castration.] [Illustration: T. H. MORGAN PLATE 8 JULIUS BIEN, N.Y. Feathers from hen-feathered male Sebright (1, 2, 3, 4) that changed to cock-feathered male (1ª, 2ª, 3ª, 4ª) after castration; and then began to go back as the testes regenerated (1ᵇ, 2ᵇ, 3ᵇ, 4ᵇ); then changed again to cock-feathering after castration (1ᶜ, 2ᶜ, 3ᶜ, 4ᶜ).] [Illustration: T. H. MORGAN PLATE 9 JULIUS BIEN, N.Y. Feathers showing complete (1) or incomplete (2 and 3) change from hen-feathering to cock-feathering (1ª, 2ª, 3ª) after castration.] [Illustration: T. H. MORGAN PLATE 10 JULIUS BIEN, N.Y. Normal. 1, 2; transitional, 1ª, 2ª, and changed-over feathers, 2ᵇ, of Sebright, 3, 4 and 5. Feathers from F₂ birds.] FOOTNOTES: [1] The expectation for 1 dominant and 1 recessive factor is so nearly the same as for 1 dominant alone that for the numbers obtained no difference between the two cases could be detected.