In this lecture, the author points out that Nägeli's perspective on the evolution of the organic world has always struck him as surprising. He assumed that it had arisen from inherent internal forces and that external influences had only played a secondary and unimportant role, improving and modifying but not determining. This astute thinker stated unequivocally that, in his opinion, the course of development would have resulted in roughly the same outcome even if life conditions had remained unchanged since the beginning.