III. Mathematical contributions to the theory of evolution.—VIII. On the inheritance of characters not capable of exact quantitative measurement.—Part I. Introductory. Part II. On the inheritance of coat-colour in horses. Part III. On the inheritance of eye-colour in man

Abstract

(1.) A certain number of characters in living forms are capable of easy observation, and thus are in themselves suitable for observation, but they do not admit of an exact quantitative measurement, or only admit of this with very great labour. The object of the present paper is to illustrate a method by which the correlation of such characters may he effectively dealt with in a considerable number of cases. The conditions requisite are the following:— (i.) The characters should admit of a quantitative order, although it may be impossible to give a numerical value to the character in any individual. Thus it is impossible at present to give a quantitative value to a brown, a bay, or a roan horse, but it is not impossible to put them in order of relative darkness of shade. Or, again, we see that a blue eye is lighter than a hazel one, although we cannot à priori determine their relative positions numerically on a quantitative scale.