The adaptations in the sense of the Darwinian laws have affected the animal’s embryonic life more and more, the higher the tree of life grew. The long recapitulation of the ancestral stages often came into conflict with the young individual’s need for protection. The result was that the biogenetic law found itself restricted by the Darwinian laws of adaptation. The too lengthy succession of ancestral portraits was abbreviated and compressed. Whole stages of embryonic or larval development were interpolated that had nothing to do with these ancestral portraits, but were destined for the protection of the fœtus. The butterfly-pupa is really an instructive instance of this description. It does not reproduce a crab-stage, nor has there been any stage in the ancestry of the butterfly when they lived throughout life in pupa-houses. The pupa is simply a later adaptation in the development of the butterfly, a protective stage in which it accomplishes the transition from the caterpillar-form in much the same way as the young bird develops under the protection of the hard egg-shell. Thus only a faint and shadowy trace has been left of the real ancestral forms, though this trace is an extremely instructive one. But we must not expect the impossible from it. In this way our naked and crude biogenetic law assumes a more finished and scientific form: the embryonic development of the individual is a condensed, abbreviated, and to some extent modified epitome of the evolutionary history of its ancestors. That is more modest, but it is a correct expression of the facts. The essential point of the older idea was not in itself wrong; all that was done was to explain the gaps, and leaps, and contradictions in it. Now that Oken’s share in the theory has been properly appreciated, we may notice another little historical detail. In the period immediately after his time these ideas were ridiculed by men of science, great and small, but they were not exactly “done to death.” Agassiz, the most pronounced creationist and dualist of all the nineteenth-century zoologists, expounded them occasionally as a curious instance of the divine action. In fact, he looked upon the whole of zoology as a mystic cabinet of curiosities—the more curious the better. Thus he came to play with this idea and confirm it, but merely took it at first as a fine figure of speech. Agassiz is a tragical form. He survived Darwin, much in the same way that many an elegant _mot-de-salon_ on the rights of man survived the French Revolution. Suddenly the whole structure of his ideas seemed to fall about him. Where he had played with roses, he now found torches. He reeled like a smitten man, and cried out against the horrid monsters that brought him pain and bitterness. His anxiety began with Darwin, even as regarded the question of the embryo. But there was another, a man far away in South America, that increased it—Fritz Müller.