| Serial No. | Pen No. | No. of mother. | Offspring. | |||
| 4-4 toes. | 4-5 toes. | 5-5 toes. | Average. | |||
| 1 | 727 803 | 2457 | 1 | 2 | 34 | 9.89 |
| 2 | 727 803 | 3105 | 1 | 0 | 45 | 9.95 |
| 3 | 803 | 2579 | ... | 1 | 12 | 9.92 |
| 4 | 727 | 3106 | ... | ... | 4 | 10.00 |
| 5 | 727 | 2494 | 1 | 0 | 5 | 9.67 |
| 6 | 727 | 2459 | ... | ... | 16 | 10.00 |
No direct relation here appears between development of the extra toe in the parents and the average number of toes in the offspring.
Of the Silkies, 3 hens were used in 5 matings. The same 6-toed cock (No. 774) was employed throughout (table 19).
Table 19.
| Serial No. | Pen No. | Mother. | f | Offspring. | ||||||||
| No. | No. of toes. | 4-4 toes | 5-4 toes | 5-5 toes | 4-6 toes | 5-6 toes | 6-6 toes | Aver- age. | ||||
| 1 | 734 815 | 499 | 6-6 | 21 | a | 2 | 1 | 7 | 0 | 3 | 8 | 10.3 |
| b | 1 | 0 | 3 | 0 | 0 | 17 | 11.4 | |||||
| 2 | 734 815 | 773 | 6-5 | 13 | a | ... | ... | 6 | 0 | 3 | 4 | 10.9 |
| b | ... | ... | 6 | 0 | 3 | 4 | 10.9 | |||||
| 3 | 734 | 500 | 5-5 | 8 | a | ... | 2 | 4 | 0 | 2 | ... | 10.0 |
| b | ... | ... | 3 | 2 | 2 | 1 | 10.5 | |||||
In table 19 the series a of observed average numbers of filial toes (10.3, 10.9, 10.0) and the series b obtained by assigning the typical full number to all reduced types (11.4, 11.4, 10.5) are decidedly irregular. There is, however, between the parental and the filial series a correlation of +0.250 ± 0.070. This indicates a slight tendency for the number of toes in the progeny to vary with those of the parentage.
The second set of data is derived from special matings made with hybrids between Houdans and 4-toed races. On the one hand, in pens 728 and 813, cocks with well-developed toes of the duplex type were mated with hens as nearly as possible of the same sort; while in pens 765, 769, and 820 cocks with small, imperfectly separated toes (probably of the duplex type[4]) were mated with hens as far as possible of the same sort.
Tables 20, 21, and 22 give in detail and in summary the distribution of types of polydactylism in the families from well-developed and in those from poorly developed parents. They show a great difference between the offspring of parents with good extra-toe (table 20) and those with poor extra-toe (table 21). The former yield over 80 per cent offspring with 5 toes or more on one or both feet, while the latter yield about 57 per cent of such.
On the other hand, in the former families there are less than half as many offspring with only 4 toes as in the latter. Classifying "reduced" forms with their proper advanced type, we find highly polydactyl parents yielding only 16 per cent non-polydactyl offspring, while slightly polydactyl parents yield 43 per cent non-polydactyl offspring. The percentage of polydactylous young diminishes with the size and distinctness of the extra toes and the grades of the polydactyl offspring are lower (absence in table 22, b, of 6 toes). Both of Castle's conclusions seem to be confirmed.