The great bull is sire of a great cow--_because he was son of a great cow_. And he is a great bull because he received from his dam a great female Vital-potential, for differentiation into greatness of the male traits that characterise great males. And in his turn, he may sire a cow greater than his mother, because in passing on to his daughter the great female Vital-potential of his mother, he passes on a female potential of greatness to which his own male inherence of greatness has added a further power of Differentiation. This increased _Male_ power of differentiation, descending in the female line, however, manifests in traits of increased _Female_ functioning--the function of milking, that is. The daughter inherits thus from her father the Female potential of her paternal grandmother, with new power of Male differentiation acquired by its residence during a generation (so to speak) in a male organisation. Which new power, when reawakened to function in a female organism, manifests in a further degree of Femaleness. Male development having progressed along lines of increasing brain- and nervous power, which the female has ever further inherited, Female development has progressed along lines of such increasing brain-power as has enabled her to transform her native simple and undifferentiated Femaleness into ever further developed and more complex Female _traits_, or functional and nervous characteristics. While, on the other hand, since Female evolution has proceeded along lines of increasing Life, or Vital Power, which the male has ever further inherited this increasing Vital power it has been that has served as _potential_ for the evolution of his Maleness in terms of higher brain- and nervous power. The great cow is mother of a great bull _because she was daughter of a great sire_. And she was a great cow because she received from her sire a great male complement of developmental power, which imparted to her Recessive, and undifferentiated Femaleness, further power of functioning as female characteristics. And she may mother a son greater even than her sire because the great male Developmental impetus of her father becomes in her a greater Vital potential; which, descending in the male line, engenders further power for the further differentiation of male characteristics. III _Evolution of Species and evolution of the Individual occur on different planes_ The Evolution of Species progresses in every generation by way of each Sex having derived from the other Sex a new and opposite potential to engender, in every alternate generation, the further evolution of its Sex-traits along its own (and contrary) lines.