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Updated: May 5, 2025
In fact, Christianity may be considered as a second creation; and the justifying cause for the constituent miracles of Christianity is even to us as apparent as any which could have operated at the primary creation. The epigenesis was, at least, as grand an occasion as the genesis.
A specially energetic fellow-worker on Eimer’s line is W. Haacke, a zoologist of Jena, author of “Gestaltung und Vererbung,” and “Die Schöpfung des Menschen und seiner Ideale.” In the first of these works Haacke combats, energetically and with much detail, Weismann’s “preformation theory,” and defends “epigenesis,” for which he endeavours to construct graphic diagrams, his aim being to make a foundation for the inheritance of acquired characters, definitely directed evolution, saltatory, symmetrical, and correlated variation.
The supporters of the first theory considered themselves much more scientific and exact than those of the second. And not without reason. For the theory of epigenesis obviously required mysterious formative principles, and equally mysterious powers of recollection and recapitulation, which impelled the undifferentiated ovum substance into the final form, precisely like that of its ancestors.
The weight of Malpighi's observations therefore fell into the scale of that doctrine which Harvey terms metamorphosis, in contradistinction to epigenesis. Mais cette imagination est bien eloignee de la nature des choses.
One of Harvey's prime objects is to defend and establish, on the basis of direct observation, the opinion already held by Aristotle; that, in the higher animals at any rate, the formation of the new organism by the process of generation takes place, not suddenly, by simultaneous accretion of rudiments of all, or of the most important, of the organs of the adult; nor by sudden metamorphosis of a formative substance into a miniature of the whole, which subsequently grows; but by epigenesis, or successive differentiation of a relatively homogeneous rudiment into the parts and structures which are characteristic of the adult.
In the words of one of the greatest of modern authorities, "We still do not know why a certain cell becomes a gland-cell, another a gangleon-cell; why one cell gives rise to smooth muscle-fiber, while a neighbor forms voluntary muscle.... It is daily becoming more apparent that epigenesis with the three layers of the germ furnishes no explanation of developmental phenomena."
Palingenesie Philosophique, part X. chap. But, thus defined, the germ is neither more nor less than the "particula genitalis" of Aristotle, or the "primordium vegetale" or "ovum" of Harvey; and the "evolution" of such a germ would not be distinguishable from "epigenesis."
But we cannot leave M. Flourens without calling our readers' attention to his wonderful tenth chapter, "De la Preexistence des Germes et de l'Epigenese," which opens thus: "Spontaneous generation is only a chimaera. This point established, two hypotheses remain: that of 'pre-existence' and that of 'epigenesis'. The one of these hypotheses has as little foundation as the other."
It is a striking example of the difficulty of getting people to use their own powers of investigation accurately, that this form of the doctrine of evolution should have held its ground so long; for it was thoroughly and completely exploded, not long after its enunciation, by Casper Friederich Wolff, who in his "Theoria Generationis," published in 1759, placed the opposite theory of epigenesis upon the secure foundation of fact, from which it has never been displaced.
On the one hand, it posits a strictly mechanistic epigenesis, and on the other hand, it incorporates the notion of "specificall vertues drawne by the bloud in its iterated courses, by its circular motion, through all the severall partes of the parents body." Digby rejects an internal agent, entelechy, or the Aristotelian formal and efficient causes.
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