1 LECTURE VII1- PART I GALTON AND THE STATISTICAL STUDY OF INHERITANCE To talk about inheritance is much easier than to study it. Of the books and essays which meet us at every turn few have much basis in research, but among the few are those of Francis Galton. His works, which have appeared at intervals during the past twenty years, are not speculations, but studies. They describe long and thorough investigations, carried out by rigorous methods, in lines laid down on a plan which has been matured with great care and forethought. The simplicity of their language is as notable as their substance. Dealing with conceptions which are both new and abstruse, their author finds our mother tongue rich enough for all his needs, and while the reasoning often taxes all our powers, there is never any doubt as to the meaning of the words. When, in rare cases, a technical term is inevitable, some familiar word is chosen with so much aptness that it does its duty, and presents the new conception better than any which half a dozen dead languages could afford. The terms, "mid-parent" or "mid," "fraternity," "nurture," and "Q" cannot mislead or convey any idea except the right one. My own debt to Galton is great, and it is acknowledged with gratitude. Such acquaintance with the statistical method as I possess, I owe to the study of these books, especially the ones on "Hereditary Genius" (1869), on "Natural Inheritance" (1889), and on "Finger Prints" (1892). My attempt to question Galton's generalizations may therefore seem ungracious and presumptuous, but the uncertainties of vital 1 A review of the works of Francis Galton; reprinted from the Popular Science Monthly for February and March, 1896. statistics are proverbial; and it is not impossible that Galton's data may fail to cover all the ground which they should in order to prove his general conclusions. One of these generalizations is so far-reaching that it must, if well founded, lead to fundamental change in our view of the origin of species. According to Darwin and Wallace, specific identity in living things is the outcome of the extermination, in the struggle for existence, of the individuals which depart too widely from that "type" which is, on the whole, the best adapted to existing conditions. As these conditions change, the type is also slowly modified through a change in the standard of extermination. According to this view, the type is the outcome of the statistical "law of error" or the deviation from the mean, that holds good in the environment; and while the "events" are properties of the organism, the type is fixed by the external world, and not by anything in the organism itself. Galton holds that specific identity is not due to the process of extermination, but to "organic stability." As I understand him, he holds that this fills up the gaps made by extermination, and thus keeps the type intact. This "principle of stability," which is held to result in the persistency of types, is said to be quite independent of selection. "Genera and species may be formed without the slightest aid from either natural or sexual selection." "Organic stability is the primary factor by which the distinctions between genera are maintained." Galton holds, furthermore, not only that specific stability is independent of selection, but that selection is "scarcely competent" to effect a change of type "by favoring mere varieties" that is, the ordinary slight differences between individuals; and that it is only when a "sport" has made its appearance, only when the type has actually changed, that selection can exert any influence. According to this view the agencies which cause sports are the real causes of the mutation of species, and natural selection can do no more than to exterminate disadvantageous sports, and thus favor advantageous ones. The "organic stability" to which so much is attributed is held to be due to the fact that the child inherits in part from its parents, and in part from more remote ancestors; and since the |