[The theory of] _Pre-established Harmony_ may proceed in two different ways. It regards every organised being as generated by one of like kind, either as an _educt_ or a _product_. The system which regards generations as mere educts is called the theory of _individual preformation_ or the theory of _evolution_: that which regards them as products is entitled the system of _epigenesis_. This latter may also be entitled the system of _generic preformation_, because the productive faculty of the generator and consequently the specific form would be _virtually_ performed according to the inner purposive capacities which are part of its stock. In correspondence with this the opposite theory of individual preformations would be better entitled the _theory of involution_. The advocates of the _theory of evolution_, who remove every individual from the formative power of nature, in order to make it come immediately from the hand of the Creator, would, however, not venture to regard this as happening according to the hypothesis of Occasionalism. For according to this the copulation is a mere formality, _à propos_ of which a supreme intelligent Cause of the world has concluded to form a fruit immediately by his hand, and only to leave to the mother its development and nourishment. They declare themselves for preformation; as if it were not all the same, whether a supernatural origin is assigned to these forms in the beginning or in the course of the world. On the contrary, a great number of supernatural arrangements would be spared by occasional creation, which would be requisite, in order that the embryo formed in the beginning of the world might not be injured throughout the long period of its development by the destructive powers of nature, and might keep itself unharmed; and there would also be requisite an incalculably greater number of such preformed beings than would ever be developed, and with them many creations would be made without need and without purpose. They would, however, be willing to leave at least something to nature, so as not to fall into a complete Hyperphysic which can dispense with all natural explanations. It is true, they hold so fast by their Hyperphysic that they find even in abortions (which it is quite impossible to take for purposes of nature) an admirable purposiveness; though it be only directed to the fact that an anatomist would take exception to it as a purposeless purposiveness, and would feel a disheartened wonder thereat. But the production of hybrids could absolutely not be accommodated with the system of preformation; and to the seeds of the male creature, to which they had attributed nothing but the mechanical property of serving as the first means of nourishment for the embryo, they must attribute in addition a purposive formative power, which in the case of the product of two creatures of the same genus they would concede to neither parent.