This theory is usually known as the "evolution theory" in Germany, in contradistinction to the "epigenesis theory.
It is not surprising that the whole of the physiologists of the second half of the eighteenth century submitted to the ruling of this physiological pontiff, and attacked the theory of epigenesis as a dangerous innovation.
In the first place, his theory of epigenesis gave us our first real insight into the nature of embryonic development.
It may be safely asserted that according to the theory of epigenesis the germ-cells cannot be influenced except as regards their nutrition.
In the latter part of the 17th century the doctrine of epigenesis thus advocated by Harvey was controverted on the ground of direct observation by M.
Wolff suggested, in 1759, that there is an epigenesis or a progressive evolution and differentiation of organs from a homogeneous primitive germ.
That then is our result: not evolutio, but epigenesis--“epigenesis vitalistica.
Indeed, every embryonic part may in some respect be a possible cause for morphogenetic events, which are to occur on every other part: it is here that the very roots of epigenesis are to be found.
To these modern preformationists are opposed the modern upholders of epigenesis or gradual differentiation, who attempt to elaborate a mechanical theory of development.
For the decision of a question so momentous as the relative scopes of evolution and epigenesis in embryology must have an important bearing on the future of biology, upon its aim and the method of research.
Wolff's epigenesis was not a complete explanation--indeed, from its fundamental conception it could not possibly be such.
It is interesting to display the essential contrast between preformation and epigenesis in the poetical words of Wolff himself.
In fact, the deepest consideration leads us again to the original question: Is embryonic development epigenesis or evolution?
The prosecution of biological investigation will continuously endow the theory of epigenesis with a fuller and fuller meaning, but will never transform it into a solution final in the sense of the theory of preformation.
Clearly, according to these general definitions, occurrences which outwardly exhibit epigenesis may be in reality partial or complete evolution.
Many embryological investigations were performed during the eighteenth century, but most relate to the controversy regarding epigenesis and preformationism as the true expression of embryonic development.
Digby's general theory thus represents a strange mixture of epigenesis and pangenesis, and is not entirely devoid of "virtues.
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.
Not long after Harvey's publication, Casper Frederick Wolf established the theory of epigenesisupon a firm foundation, where it still remains.
Epigenesis consists in the successive differentiation from the relatively homogeneous elements as found in the egg, to the complicated parts and structure as seen in the offspring.
We see how with these gentlemen the wisdom of the recitation-room regarding the infallibility of epigenesis has grown into a dogma, and whoever ventures to disturb its foundations must be burnt as a heretic.
A real {58} epigenesis from absolutely homogeneous and not merely like units is not thinkable.
It is customary now to look upon the preformation-theory of Bonnet as a discarded monstrosity, and on the epigenesis of K.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "epigenesis" in a variety of sentences. We hope that you will now be able to make sentences using this word.
