| +----+---+----+----+----+----+---+---+---+---+---+--------+ |Total (851)| 105| 61| 108| 178| 127| 109| 62| 37| 32| 20| 12| 3.59 | |Per cent. |12.3|7.2|12.7|20.9|14.9|12.8|7.3|4.4|3.8|2.3|1.4| ... | +-----------+----+---+----+----+----+----+---+---+---+---+---+--------+ TABLE 43.--_DD x DD (Silkie crosses)._ +-----------+----------------------------+ | | Boot-grade in offspring. | |Serial No. +----+----+----+----+--------+ | | 0 | 1 | 2 | 3 |Average.| +-----------+----+----+----+----+--------+ | 117 | 2| ..| ..| 1| 1.00 | | 118 | ..| 1| ..| ..| 1.00 | | 128 | 26| 6| 1| 1| 0.32 | | 130 | 11| 4| ..| ..| 0.27 | | 131 | 18| 2| 1| ..| 0.19 | | 132 | 19| ..| ..| ..| 0.0 | | 133 | 33| ..| ..| ..| 0.0 | | 134 | 8| ..| ..| ..| 0.0 | | 135 | 19| ..| ..| ..| 0.0 | | 136 | 16| ..| ..| ..| 0.0 | | +----+----+----+----+--------+ |Total (169)| 152| 13| 2| 2| 0.14 | |Per cent. |89.9| 7.7| 1.2| 1.2| .... | +-----------+----+----+----+----+--------+ The significance of the data given in tables 39 to 43 is best brought out by summarizing them. Especially instructive is a comparison of the pure-bred with the hybrids. Since the data are most complete in the case of the Brahma crosses, these will be considered in most detail. So far as they go, the results with the Cochins and Silkies are entirely confirmatory. Table 44 shows clearly, first, that there are families of two booted parents that never fail to produce booted offspring. There is, however, even in pure-bred booted races, a marked variability in the grade of booting, extending from 3 (or 4) to 10. The significance of this variability must be left for future investigations. There is in the least boot, as it were, an extension of the field of activity of the feather-inhibiting factor that is always present on the hinder aspect of the shank, so that it interferes with the development of feathers on the inner face of the shank also. In the first hybrid generation all somatic cells are hybrid. The feather inhibitor is present in the skin of the shank, but its strength is diluted by the presence in the same cells of a protoplasm devoid of the inhibiting property. Consequently, the prevailing grade of the boot falls from 6 (or 10) to 3. Despite the dilution, inhibition is complete in about 8 per cent of the offspring (grade 0); in about 10 per cent of the offspring the inhibiting factor is so weak that the boot develops as in the pure-blooded Brahma. When, as a result of inbreeding F1's, the feather-inhibiting factor is eliminated from certain offspring, and such full-feathered birds are bred together, we find a return of the mode to high numbers, such as 8 to 10 (but also 5). There is no doubt of segregation.