Theory Of Epigenesis:-
This theory was proposed by Wolff. This theory is an antithesis of Preformation theory.
According to this theory is no Preformed of the individual in the ovum or sperm. Wolff explanation are based on the observation of the development of chick embryos. He published the results of his observation in 1759 . In a comprehensive volume and title THEORIA generation. He observe that embryo develop by progressive growth and differentiation. The material from which the embryo formed of in granular substance.
These granules during development are arranged to form cellular layer called germinal layer. These layer grow thick called germinal layer. These layer grow thick in some parts, grow thin on some other parts and turn into pocket, grow thin on some other parts and turn into pocket in other parts and attest become the body of the embryos.
Wolff finding seriously opposed by Haller and Bannet the controvercy continue until mackel. Who pointed out in 1821 the correctness of Wolff ‘s observation and conclusion. Then only the theory of Epigenesis was accepted after the discovery of protoplasm in animal cell by Dujardin in animals the acceptance of theory spread rapidly Wolff ‘s epigenetic theory was confirm by great embryologist yearly 19th . Century von bear the father of modern embryology.