It seems clear that organic beings must be exposed during several generations to new conditions to cause any great amount of variation; and that, when the organisation has once begun to vary, it generally continues varying for many generations.
Garbi dagoela dirudi izaki organikoek, aldakuntza inportanteren bat gerta dakien, baldintza berrien pean izan behar dutela zenbait belaunaldiz eta, behin organismoa aldatzen hasten denean, aldatzen segitzen duela eskuarki belaunaldi askotan zehar.