I. Family likeness in eye-colour

My inquiry into Family Likeness in Stature (ante, p. 42) enabled me to define, in respect to that particular quality, the relation in which each man’s peculiarity stands to those of each of his ancestors. The object of the present memoir is to verify that relation with respect to another quality, namely, eye-colour. Speaking of heritage, independently of individual variation, and supposing female characteristics to be transmuted to their male equivalents, I showed (1) that the possession of each unit of peculiarity in a man [that is of difference from the average of his race] when the man’s ancestry is unknown, implies the existence on an average of just one-third of a unit of that peculiarity in his “mid-parent,” and, consequently, in each of his parents; also just one-third of a unit in each of his children; (2) that each unit of peculiarity in each ancestor taken singly, is reduced in transmission according to the following average scale:—from a parent, to ¼; from a grandparent, to 1/16; from a great-grandparent, to 1/64, and so on.