I. Haeckel and His Opponents

How great the prejudices are that the idea of evolution had to face was clearly shown by the reception which Caspar Friedrich Wolff's Theoria Generationis, which appeared in 1759, met with among the men of science who accepted Haller's views. It was demonstrated in this book that in the human ovum not even a trace of the form of the developed organism is present, but that its development consists in a series of new formations. Wolff defended the idea of a real evolution, an epigenesis, a becoming from what is not present, as against the view of seeming evolution. Haeckel says of Wolff's book that it “belongs, in spite of its small size and awkward language, to the most valuable writings in the whole field of biological literature. ...” Nevertheless, this remarkable book had at first no success whatever. Although scientific studies, as a result of the stimulus imparted by Linnaeus, flourished mightily at that time, although botanists and zoologists were soon counted no longer by dozens but by hundreds, yet no one troubled himself about Wolff's Theory of Generation. The few, however, who had read it, held it to be fundamentally wrong, and especially Haller. Although Wolff proved by the most accurate observations the truth of epigenesis, and disproved the current hypotheses of the preformation doctrine, nevertheless the “exact” physiologist Haller remained the most zealous follower of the latter and rejected the correct teaching of Wolff with his dictatorial edict: “There is no becoming” ( Nulla est epigenesis!). With so much power did human thinking set itself against a view, of which Haeckel (in his Anthropogenesis) remarks: “To-day we can hardly any longer call this theory of epigenesis a theory, because we have fully convinced ourselves of the correctness of the fact, and can demonstrate it at any moment with the help of the microscope.”