Table 20.—Distribution of toe-types in the offspring of "good" extra-toed parents.
| Serial No. | Pen No. | Mother. | Father. | Mating. | Absolute numbers. | Theoretical classification. | |||||||||||||||||||
| No. | Gen. | Races. | No. | Gen. | Races. | 4-4 | 4-5 | 5-5 | 5-6 | 6-6 | Average. | ss. | sd. | d'd'. | d'd. | dd. | d't'. | dt'. | dt. | t't'. | tt. | q't. | |||
| 1 | 728 | 2271 | F2 | Wh. Legh. × Houd. | 258 | F1 | Houd. × Wh. Legh. | DD × DR | 4 | 1 | 21 | ... | ... | 9.65 | 3 | ... | 1 | 1 | 21 | ... | ... | ... | ... | ... | ... |
| 2 | 728 | 912 | F2 | Do. | 258 | F1 | Do. | DR × DR | 5 | 3 | 21 | ... | ... | 9.55 | 5 | 3 | ... | ... | 20 | ... | 1 | ... | ... | ... | ... |
| 3 | 728 | 2248 | F2 | Do. | 258 | F1 | Do. | DD × DR | 8 | 3 | 22 | ... | ... | 9.42 | 8 | 3 | ... | ... | 21 | ... | ... | ... | 1 | ... | ... |
| 4 | 728 | 2272 | F2 | Do. | 258 | F1 | Do. | DR × DR | 17 | 4 | 34 | ... | ... | 9.31 | 17 | 1 | ... | 3 | 34 | ... | ... | ... | ... | ... | ... |
| 5 | 728 | 174 | F1 | Do. | 258 | F1 | Do. | DR × DR | 10 | 1 | 15 | ... | ... | 9.19 | 10 | 1 | ... | ... | 14 | ... | 1 | ... | ... | ... | ... |
| Totals (169) | 44 | 12 | 113 | ... | ... | 9.41 | 43 | 8 | 1 | 4 | 110 | 0 | 2 | 0 | 1 | ... | ... | ||||||||
| Percentages | 26.0 | 7.1 | 66.9 | ... | ... | ... | 25.4 | 4.7 | 0.6 | 2.4 | 65.2 | ... | 1.2 | ... | 0.6 | ... | ... | ||||||||
| 6 | 813 | 2271 | F2 | Wh. Legh. × Houd. | 3904 | F3 | Houd. × Wh. Legh. | D × D | ... | 2 | 32 | ... | ... | 9.94 | ... | ... | ... | 2 | 32 | ... | ... | ... | ... | ... | ... |
| 7 | 813 | 5113 | F2 | Do. | 3904 | F3 | Do. | D × D | 2 | 1 | 32 | 1 | ... | 9.89 | ... | ... | 2 | 1 | 32 | ... | ... | 1 | ... | ... | ... |
| 8 | 813 | 377 | F2 | Do. | 3904 | F3 | Do. | DR × D | 2 | 5 | 17 | ... | 1 | 9.68 | 2 | 2 | ... | 3 | 16 | ... | 1 | ... | ... | 1 | ... |
| 9 | 813 | 5122 | F3 | Do. | 3904 | F3 | Do. | D × D | 1 | 3 | 7 | ... | ... | 9.55 | 1 | 3 | ... | ... | 7 | ... | ... | ... | ... | ... | ... |
| 10 | 813 | 935 | F2 | Do. | 3904 | F3 | Do. | DR × D | 1 | 2 | 25 | 1 | 1 | 9.53 | 1 | 2 | ... | ... | 25 | ... | ... | 1 | ... | ... | 1 |
| 11 | 813 | 2272 | F2 | Do. | 3904 | F3 | Do. | DR × D | 5 | 2 | 18 | ... | ... | 9.52 | 4 | 1 | 1 | ... | 18 | 1 | ... | ... | ... | ... | ... |
| 12 | 813 | 912 | F2 | Do. | 3904 | F3 | Do. | DR × D | 4 | 5 | 11 | ... | ... | 9.35 | 3 | 5 | 1 | ... | 11 | ... | ... | ... | ... | ... | ... |
| 13 | 813 | 7320 | F3 | Do. | 3904 | F3 | Do. | DR × D | 5 | 1 | 11 | ... | ... | 9.35 | 3 | 1 | 2 | ... | 11 | ... | ... | ... | ... | ... | ... |
| 14 | 813 | 5142 | F3 | Do. | 3904 | F3 | Do. | DR × D | 2 | 1 | 4 | ... | ... | 9.28 | 2 | ... | ... | 1 | 4 | ... | ... | ... | ... | ... | ... |
| Totals (205) | 22 | 22 | 157 | 2 | 2 | 9.70 | 16 | 14 | 6 | 7 | 156 | 1 | 1 | 2 | 0 | 1 | 1 | ||||||||
| Percentages | 10.7 | 10.7 | 76.5 | 1.0 | 1.0 | ... | 7.8 | 6.8 | 2.9 | 3.4 | 76.2 | 0.5 | 0.5 | 1.0 | ... | 0.5 | 0.5 | ||||||||
Table 21.—Distribution of toe-types in the offspring of "poor" extra-toed parents.
| [A] No. 2016 has 4-4 toes and is a hybrid between a 5-toed White Leghorn × Houdan and a 4-toed Minorca × Polish. | ||||||||||||||||||||
| Serial No. | Pen No. | Mother. | Father. | Mating. | Absolute numbers. | Theoretical classification. | ||||||||||||||
| No. | Gen. | Races. | No. | Gen. | Races. | 4-4 | 4-5 | 5-5 | 5-6 | Average. | ss. | sd. | d'd'. | d'd. | dd. | d't'. | dq'. | |||
| 1 | 765 | 984 | F2 | Wh. Legh. × Houd. | 1794 | F2 | Wh. Legh. × Houd. | DR × DR | 9 | 5 | 11 | ... | 9.08 | 9 | 3 | ... | 2 | 10 | 1 | ... |
| 2 | 765 | 1790 | F2 | Do. | 1794 | F2 | Do. | DR × DR | 18 | 7 | 17 | ... | 8.98 | 18 | 6 | ... | 1 | 17 | ... | ... |
| Totals (67) | 27 | 12 | 28 | ... | 9.02 | 27 | 9 | ... | 3 | 27 | 1 | ... | ||||||||
| Percentages | 40.3 | 17.9 | 41.8 | ... | ... | 40.3 | 13.4 | ... | 4.5 | 40.3 | 1.5 | ... | ||||||||
| 3 | 769 | 492 | F1 | Wh. Legh. × Houd. | 911 | F2 | Wh. Legh. × Houd. | DR × DR | 13 | 1 | 14 | ... | 9.04 | 13 | 1 | ... | ... | 14 | ... | ... |
| 4 | 769 | 4976 | F2 | Do. | 911 | F2 | Do. | DR × DR | 11 | 3 | 9 | ... | 8.91 | 11 | 3 | ... | ... | 8 | 1 | ... |
| 5 | 769 | 2254 | F2 | Do. | 911 | F2 | Do. | DR × DR | 22 | 6 | 8 | ... | 8.61 | 22 | 4 | ... | 2 | 8 | ... | ... |
| 6 | 769 | 1305 | F2 | Do. | 911 | F2 | Do. | DR × DR | 12 | 1 | 4 | ... | 8.53 | 12 | ... | ... | 1 | 4 | ... | ... |
| Totals (104) | 58 | 11 | 35 | ... | 8.77 | 58 | 8 | ... | 3 | 34 | 1 | ... | ||||||||
| Percentages | 55.8 | 10.6 | 33.7 | ... | ... | 55.8 | 7.7 | ... | 2.9 | 32.7 | 1.0 | ... | ||||||||
| 7 | 820 | 984 | F2 | Wh. Legh. × Houd. | 4731 | F3 | Wh. Legh. × Houd. | D × DR | 2 | 3 | 27 | ... | 9.78 | 2 | 2 | ... | 1 | 27 | ... | ... |
| 8 | 820 | 2255 | F2 | Do. | 4731 | F3 | Do. | DR × DR | 6 | 1 | 10 | ... | 9.24 | 6 | ... | ... | 1 | 10 | ... | ... |
| 9 | 820 | 6479 | F3 | Do. | 4731 | F3 | Do. | DR × DR | 12 | 2 | 16 | ... | 9.13 | 10 | 1 | 2 | 1 | 15 | 1 | ... |
| 10 | 820 | 2016 | F1[A] | Do. | 4731 | F3 | Do. | DR × DR | 9 | 2 | 2 | ... | 8.45 | 9 | 2 | ... | ... | 2 | ... | ... |
| Totals (92) | 29 | 8 | 55 | ... | 9.28 | 27 | 5 | 2 | 3 | 54 | 1 | ... | ||||||||
| Percentages | 31.5 | 8.7 | 59.8 | ... | ... | 29.3 | 5.4 | 2.2 | 3.3 | 58.7 | 1.1 | ... | ||||||||
But a more critical examination of the parentages of the 5 pens shows that they are not comparable. In matings 6 to 14 of table 20 the cock is almost certainly a dominant in respect to toes; whereas the cocks in table 21 are probably heterozygous. The heterozygous state determines two things: the imperfect nature of the extra-toe and a relative deficiency in the offspring of the higher toe-numbers. In our results we can not say that one of these things is the cause of the other, as Castle does; they are, rather, in all probability, due to a common cause. I think Castle's paper may justly be criticized for not giving sufficient data concerning the ancestry of the individual mothers used. Without such data the paper can not be said satisfactorily to demonstrate his conclusion.
Table 22.—Summary of observed toe-numbers in offspring, percentages.
| a. Parents have "good" extra toes. | b. Parents have "poor" extra toes. | ||||||||
| Pen No. | 4-4 toes. | 4-5 toes. | 5-5 toes. | 5-6 toes. | 6-6 toes. | Pen No. | 4-4 toes. | 4-5 toes. | 5-5 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. [28]