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"The doctrine of epigenesis is derived from Harvey: following by ocular inspection the development of the new being in the Windsor does, he saw each part appear successively, and taking the moment of appearance for the moment of formation he imagined epigenesis."
Actually, Harvey's exposition of epigenesis, albeit clear, is not totally impressive, since it is largely a reflection of Aristotle's influence. The main importance of Harvey's vigorous and cogent defense of epigenesis is that it provided some kind of counterbalance to the increasingly dominant preformationist interpretations of embryonic development.
Haller, the ovulist, who had great authority as a physiologist, in a famous work, Elementa physiologiae, upheld the principle vigorously: "Nulla est epigenesis. 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.
So far as individual plants and animals are concerned, therefore, evolution is not a speculation but a fact; and it takes place by epigenesis.
In fact, the main concern of Harvey's wonderful little treatise is not with generation, in the physiological sense, at all, but with development; and his great object is the establishment of the doctrine of epigenesis.
To the theory as a whole, because of its fundamental conception of preformation, and to its subsidiary hypotheses, piece by piece, there has been energetic opposition on the part of the upholders of the modern mechanical theory of epigenesis.
In the latter part of the seventeenth century, the doctrine of epigenesis, thus advocated by Harvey, was controverted, on the ground of direct observation, by Malpighi, who affirmed that the body of the chick is to be seen in the egg, before the punctum sanguineum makes it appearance.
Digby's general theory thus represents a strange mixture of epigenesis and pangenesis, and is not entirely devoid of "virtues."
In the present case, a delicate physiological problem has become as popular as theories on epigenesis, spontaneous generation, or Darwinian evolution, and for an analogous reason. As the latter are expected to decide in the doctrines of natural or revealed religion, so the former is supposed to have a casting vote in regard to the agitating claims for the extension of new powers to women.
They are usually associated with a denial of the theory of natural selection, and with theories of “Orthogenesis,” “Heterogenesis,” and “Epigenesis.” We shall discuss them later when we are considering the factors in evolution. But we must first take notice of a work in which the theories opposed to Darwinian orthodoxy have been most decisively and aggressively set forth.