variability is in some manner excited, but it is the will of man which accumulates the variations in certain direction; and it is this latter agency which answers to the survival of the fittest under nature.
aldagarritasuna nolabait kilikarazten da, baina gizakiaren nahia da aldakuntzak norabide jakinean metatzen dituena, eta azken egintza hauxe da natur egoeran egokienen biziraupenari dagokiona.