This theory certainly contains all the monstrosities of preformation in the germ, the mythologies of the infinitely small, and it suffers shipwreck in ways as diverse as the number of its sides and parts.
The most subtle of these, on the side of consistent Darwinism, is that of Weismann, a pronounced preformation theory which has been increasingly refined and elaborated in the course of years of reflection.
Later he rejects both preformation and epigenesis, as mechanical distortions of vital processes.
A step towards the mechanical solution of this problem was indicated in the "preformation theory" advanced by Leibnitz, and elaborated by Bonnet.
Opposed to this theory was one of later growth, the theory of epigenesis, which maintained that the organism developed withoutpreformation from the still undifferentiated and homogeneous substance of the egg.
A theory of preformation alone affords the possibility of an explanation: an epigenetic theory is utterly unable to render any assistance in reaching an interpretation.
In modern times the theory of preformation has been revived in a less crude form, as is shown by the ideas of Nägeli, and by Darwin’s ‘pangenesis.
The opposing views of to-day were in existence centuries ago, and they are known in the history of science as the theory of preformation or evolution, and the theory of epigenesis.
It is interesting to display the essential contrast between preformationand epigenesis in the poetical words of Wolff himself.
If only, like Hertwig, one assumes to be present in the germinal material a prearrangement of qualitatively different idioblasts, one has steered into the harbour of preformation with all sails set.
Thus, the theory of preformation gave rise to the conception that living things were a series of cases or wrappings, germ folded within germ.
In a striking fashion Roux[1] has contrasted the opposing ideas inherent in our modern conception of development, but yet identical with those which formerly found expression in the theories of preformation and epigenesis.
It seems to me that the significance of Wolff's doctrine lies in this: it rejected the purely formal theory of preformation because actual observations were against it.
Moreover, in deciding between the alternatives--preformation and epigenesis--I believe that it will profit us to start our critical investigation with the cell itself.
That it might satisfy our human craving for final causes, the theory of preformation had to be accompanied by a corresponding explanation of the origin of the miniatures.
In this respect it is like its predecessor, the theory of preformation of the eighteenth century.
Germ within germ, in ever smaller miniature, after the fashion of an infinite juggler's box, was the corollary logically appended to this theory of preformation and unfolding.
In this connection the experiments which he made on the hen's egg[103] in order to produce artificial monstrosities are significant, though his purpose was rather to obtain proof of the inadequacy of the preformation hypothesis.
But the first takes place in the preformation of organic bodies, or rather of all bodies, since there is organism everywhere, although all masses do not compose organic bodies.
And I would have added that nothing is better qualified than the preformation of plants and of animals to confirm my System of Pre-established Harmony between the soul and the body.
In any case, we can state today that the cytoplasm contains the rough preformation of the future embryo.
Hence the unfertilized egg contains already a rough preformation of the embryo inasmuch as the main axis of the embryo and the arrangement of its first organs are determined.
This was the condition of things when suddenly, in 1759, Caspar Friedrich Wolff appeared, and dealt a fatal blow at the whole preformation theory with his new theory of epigenesis.
There is no trace whatever of preformationor in-folding of organs.
In fact, the preformation theory held that the germs of the whole of humanity were stored already in Eve's ova.
Among the philosophers of the time the distinguished Leibnitz was the chief defender of the "preformation theory," and by his authority and literary prestige won many adherents to it.
At the time, the "preformation theory" was probably the most widely accepted--i.
Supported by a series of most laborious and painstaking observations, he proved the entire falsity of the dominant theories of preformation and scatulation.
Let us first cast a historical glance at the older ontogeny, and the theory of preformation which is connected with it.
Closely connected with the preformation theory, and as a logical consequence of it, there arose in the last century a further theory which keenly interested all thoughtful biologists--the curious "theory of scatulation.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "preformation" in a variety of sentences. We hope that you will now be able to make sentences using this word.
