Haller, the ovulist, who had great authority as a physiologist, in a famous work, _Elementa physiologiae_, upheld the principle vigorously: "_Nulla est epigenesis. Nulla in corpore animale pars ante aliam facta est et omnes simul creatae existunt_" (nothing is created anew, no part of the human body is made before any other part, all are created at the same time). Making a calculation based on Biblical cosmogony of the number of human beings who were packed in the ovaries of Eve, he reckons them at two hundred thousand millions. Such was the state of thought when in 1759 K. F. Wolff published some of his studies in the work _Theoria generationis_, where he maintained, on the strength of experiments and microscopic observations made on the embryos of fowls, that new organisms are not pre-formed, but that they create themselves entirely, starting from nothing--that is, from a microscopic cell, simple as are all primitive cells. He described the simple process by which the real evolution of individuals is brought about: from a single cell, by division, two, and then four and then eight, are formed, and so on. And the cells thus germinated divide themselves into two or three tiny folds of "primitive folioles" from which all the organs are evolved, beginning with the alimentary canal. "This assertion," says Wolff "is not a fanciful theory; it is a description of facts collected by means of the most trustworthy observations." [Footnote 8: From Haeckel's _Anthropogenie_.] All the scientists of his day knew and made use of the microscope; all might have taken an egg, that is, the embryo of a fowl, as a subject for observation; they were not indifferent to the problem of individual genesis, but in their case it had merely excited the most complex efforts of the imagination, and had divided them into factions, as adversaries in a battle of thought. Could any one of them attempt to experiment and observe save at the risk of destroying himself together with his adversaries, as Samson destroyed himself with the Philistines? The possibility that there might be some truth in what had been seen and described, and that it might recur, should indeed have induced some one to venture upon a road which, if it proved to be the right one, would have been a glorious path to a future of discoveries and distinctions. But no. A dense fog obscured all minds, and the dazzling truth could not pierce it; thus all progress in embryology was precluded. Fifty years had passed, and Wolff, poor and persecuted, had died at Petrograd, an exile from his native land, when Pander and Ernest von Baer grappled anew with the theory of "blastodermic foliation." Then the scientific world _perceived_ the truth and accepted the evidence, inaugurating those studies in embryology which shed so much luster on the nineteenth century.