done upon inheritance by Pearson and his coworkers seems to the writer to involve from its very beginning- a fundamental biological assumption. This assumption is that a correct determination of the correlation in respect to external, somatic characters between genetically related individuals, is an adequate measure of the intensity of inheritance between these individuals. But the validity of this assumption has never been demonstrated, and presumably never can be, because such an assumption is contrary to demonstrated biological facts, which can at any time be experimentally verified. The facts to which I allude are those upon which rest the demonstration of the existence of genotypes as opposed to phaenotypes in respect to the behavior of characters in inheritance[1].
These facts in general show that the « somatic » and the « germinal » conditions or states with reference to a particular character may be quite different in the same individual. It results, then, that the « somatic » condition of such a character in the progeny has no direct or necessary relation to the « somatic » condition of the same character in the parent. Nothing is brought out more clearly by all recent experimental studies of inheritance than that the somatic condition of a character in a particular organism is a very unreliable criterion of the probable condition of that character in the progeny of that organism. Thus, to take some concrete instances by way of illustration, if one breeds a Cornish Game cock bird to a Barred Bock female the female offspring resulting will not be, in respect to plumage, colour and pattern, in the slightest degree like either parent. On the contrary they will be solid black in colour[2] . A knowledge of the « somatic » condition of the parents, in such a case, no matter how detailed it might be, would, in advance of the actual breeding test, give no clue whatever as to the probable somatic condition of its offspring. Yet, in its procedure of correlating parent and offspring in respect to somatic characters, the « law of ancestral
inheritance » definitely assumes that the somatic condition of the
