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Without pressing these objections, but on the contrary, conceding for the nonce and for argument's sake, to molecular polarity, to immanent properties, to Epigenetic evolution, all the efficacy claimed for them, I limit myself to inquiring what causes the various tendencies and directions which these imply. Tendency pre-supposes impulse; direction control.
Lett us then confidently conclude, that all generation is made of a fitting, but remote, homogeneall compounded substance: upon which, outward Agents working in the due course of nature, do change it into an other substance, quite different from the first, and do make it lesse homogeneall then the first was. Digby thus makes a good statement of epigenetic development.
His statement of epigenetic development is clear: In the egg ... there is no distinct part or prepared matter present, from which the fetus is formed ... an animal which is created by epigenesis attracts, prepares, elaborates, and makes use of the material, all at the same time; the processes of formation and growth are simultaneous ... all its parts are not fashioned simultaneously, but emerge in their due succession and order ... Those parts, I say, are not made similar by any successive union of dissimilar and heterogeneous elements, but spring out of a similar material through the process of generation, have their different elements assigned to them by the same process, and are made dissimilar ... all its parts are formed, nourished, and augmented out of the same material.
Oscar Hertwig, de Vries, Driesch and others attempt to reconcile the preformationist and the epigenetic standpoints, and “to extract what is good and usable out of both.” Hertwig and Driesch, however, can only be mentioned with reservations in this connection.
Ay, the aurelia-born image of grace sees a difference when it looks from the sun to the epigenetic thing which He raises out of corruption. There was, in that small place of skulls, a rehearsal of the great day. We hear little of these freaks now-a-days; but it was different then, when men made themselves demons by drink.
His description of chick development is of epigenetic bent: ...you may lay severall egges to hatch; and by breaking them at severall ages you may distinctly observe every hourely mutation in them, if you please. The first will bee, that on one side you shall find a great resplendent clearnesse in the white.
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