+-------------------------------------------++-----------------------------+ | _a._ Parents have "good" extra toes. || _b._ Parents have "poor" | | || extra toes. | +--------+------+------+------+------+------++--------+------+------+------+ | | 4-4 | 4-5 | 5-5 | 5-6 | 6-6 || | 4-4 | 4-5 | 5-5 | | Pen No.| toes.| toes.| toes.| toes.| toes.|| Pen No.| toes.| toes.| toes.| +--------+------+------+------+------+------++--------+------+------+------+ | 728 | 26.0 | 7.1 | 66.9 | .. | .. || 765 | 40.3 | 17.9 | 41.8 | | 813 | 10.7 | 10.7 | 76.5 | 1.0 | 1.0 || 769 | 55.8 | 10.6 | 33.7 | | | | | | | || 820 | 31.5 | 8.7 | 59.8 | | +------+------+------+------+------++ +------+------+------+ |Average.| 17.7 | 9.1 | 72.2 | 0.5 | 0.5 ||Average.| 43.2 | 11.8 | 44.9 | +--------+------+------+------+------+------++--------+------+------+------+ To summarize: "Potency," as measured by dominance of the extra-toed condition, is inherited, in the Houdan crosses at least. There is some evidence, derived from "pure-bred" Silkies, that differences in the degree of development of the extra-toes are inherited. But the average condition of the toes in the offspring of second or later generation hybrids can not be used as evidence of inheritance of the degree of parental development of the toes, since these are dependent on the same basal cause, namely, the hidden gametic constitution of the parents. Despite the obscuration of imperfect dominance, polydactylism in poultry proves itself to be a unit-character that segregates. CHAPTER III. SYNDACTYLISM. A. STATEMENT OF PROBLEM.