Comparing tables 45 to 54, we see that recessive parents are characterized by a low grade of nostril and they, of course, tend to produce offspring with a low grade. Similarly, dominants have a high grade and tend to produce offspring of the same sort, while heterozygous parents are of intermediate grade and their children have nostril grades that are, on the average, intermediate. Without regarding the gametic constitution, we might conclude, with Castle, that offspring inherit the grade of their parents, and consequently it would be possible to increase the grade, perhaps indefinitely, by breeding from parents with the highest grade. Considering the gametic constitution of the parents, it is obvious that such a conclusion is premature. To get an answer to the question it is necessary to find if there is, inside of any one table, among parents of the same gametic constitution, any such relation between parental and filial grades. This can be determined by calculating the correlation between the grades of parents and progeny. Such calculation I have made for table 48 with the result: index of correlation, _r_ = 0.018 ± 0.032, which is to be interpreted as indicating that no correlation exists; and in so far the hypothesis of Castle proves not to apply in the cases of booting and doubt is thrown on the significance of his conclusion. Finally, if we throw together the frequency distributions of all tables into one table (table 55; compare fig. B) we shall find the totals instructive. Table 55 shows that, when all results are thrown together, including hybrids of all sorts, grade 2 and grade 9 are the most frequent and grade 6 is the least frequent, the frequency gradually rising towards the extremes of the series. The same result appears in the individual series that range from grade 1 to grade 10. What is the meaning of this result? It seems to me to bear but one interpretation, namely, that there are only two centers of stability--about grades 1 and 9--and true blending of these grades, giving an intermediate condition, does not occur. Otherwise, in consequence of the repeated hybridization, the intermediate grades must be the commonest instead of the rarest. There is alternative inheritance of the nostril height. TABLE 55.--_Summary of tables 45 to 54._