13. The color of the F₁ birds is shown in plate 2, figs. 1 and 2. In general, the feathers are stippled, black and light yellow being the two most conspicuous ingredients. Since hen-feathering dominates, the dimorphism is absent, or at least is so slight as to not attract attention--little more, in fact, than in the Sebright race. The carriage of the male is like that of the Sebright male. The F₁ male and female are alike in the direct cross and the reciprocal, or at least no conspicuous difference is found between the two classes of hens, indicating that no important sex-linked factors are involved in the cross. 14. The F₂ birds show a great variety of color and pattern, but those obtained can be approximately grouped into 16 classes. The classes are, however, admittedly not uniform, indicating minor factors not here reckoned with. The classification of the hens is easiest; the F₂ hen-feathered males can then in many cases be referred to the proper classes; the F₂ cock-feathered males can not be accurately classified with their corresponding hens, except in the case of those that resemble the two P₁ males, the F₁ male, and those that castration experiments of the hen-feathered males have shown to belong to certain hen types. 15. Despite the admitted difficulties of classification, it is suggested that three factor-pairs of differences will cover the main color classes seen in the F₂ and in the back-cross. One or two of these seem to be incompletely dominant, since the F₁ birds are not like either parent in any single character, nor are they like the wild type in so far as this is represented by the game. 16. A histological examination of the testis of the male Sebright by Boring and Morgan has shown that it contains cells like those present in the ovary of all breeds of poultry. These cells are called luteal cells by Pearl and Boring, from their resemblance to the cells of that name found in the corpora lutea of mammals. In the mammals similar cells are supposed to produce internal secretions that act as hormones. Their function in the female bird is unknown, but the fact that after the removal of the ovary the female develops the secondary sexual plumage of the male suggests that some secretion from these cells performs this function. Their occurrence in the male Sebright and their complete absence, or paucity, in the males of other races supports strongly the view that these cells are concerned with the suppression of the secondary sexual plumage.