Preformation Theory

Preformation theory is an ancient theory giving an interesting  explanation of the development of an organism.It was proposed by Malpighi.According to this theory the Ovum or gametes  contain in them a mini preformed embryo.Malpighi stated that the ovum contains a miniature adult animal called homunculus.During development the homunculus expands and increases in size

Leeuwenhock in 1677 believed that the preformed embryo is inside the sperm.These scientists are called animalculists


  In parthenogenesis the egg develops into an animal without the assistance of spermatozoon.If the egg can develop with out fertilization .The embryo can not be preformed inside the spermatozoon.Anyhow this theory is not at all accepted.

Note: Animalcule is the old name of sperm.
There  are two groups of scientist Animalculists and Ovists.