These tables yield several points of interest. First, although the proportions of normal and extra toe in table 12, _a_ and _c_, are not Mendelian, yet the average _increase_, from F1 to F2 in the proportion of the recessive (4-toed) type is almost exactly what is called for by Mendel's law. That law calls for an increase of 25 per cent. The actual average increase is 23.3 per cent (20.1 and 26.5 in the two cases). It seems fair to conclude, consequently, that Mendel's law does hold here, and that the 4-toed individuals of F1 are heterozygotes with imperfect dominance. The feet of most of the 4-toed Silkies of this generation belong, indeed, to the reduced 5-toed type (table 10, B), and the reduced condition is _prima facie_ evidence of heterozygotism. In F1 Silkies of the first hybrid generation, 20 per cent of the feet exhibit "reduced" types of toes, but in F2 only 5 per cent; and this might have been anticipated, since in F2 heterozygotes are relatively only half as numerous as in F1. Again, in F2 we see reappearing the high ancestral toe-numbers (practically lost in the heterozygotes of F1, table 12, _b_). These I interpret as extracted dominants. 6-toed extracts are more numerous among the Silkie than the Houdan hybrids, because the Silkie ancestors were 6-toed and the Houdan ancestors only 5-toed. However, only a small proportion of the extracted Silkie dominants have as many toes as the original Silkie ancestors, and this indicates a permanent regression (through the contaminating influence of hybridization?) toward the normal condition of toes. It will be observed that, although 6 toes are not found in the Silkie hybrids of F1, many of these heterozygotes are of the reduced triplex type. Classifying them as virtually 6-toed, we find (table 12, _c_) 14.5 per cent of the 6-toed type in the F1 generation. Among the extracted dominants of F2 are a few showing more toes than appeared in the ancestors (table 12, _a_; there was also one 7-toed F2 Silkie hybrid, not recorded in the table). It is this sort of an advance in F2 that permits the breeder to make a forward step. Theoretically, the appearance of this more aberrant class is probably due to the greater numbers of progeny than of ancestors, since the extracted dominants of F2 are seven times as numerous as their extra-toed grandparents. Here, as elsewhere, the absolute range of variability depends upon the number of individuals observed. TABLE 13.--_Distribution of toe-numbers in the offspring of DR × R matings._