Preformation Theory (1632-1723)
(i) Scientist 'Malpighi Swammerdam' propounded the preformation theory. This theory holds that the sex cells (sperm and ova) had the miniature copy of adults and the development of embryo was actually only the enlargement of parts that were already present in the sperm or egg.
(ii) This miniature form of the animal present in the gamete was called 'Homunculus'.
(iii) This theory was supported by Hartsoeker.
(iv) Those who considered homunculus to be present is sperms were called Spermist.
(v) Leeuwenhoek & Hartsoeker believed that miniature of organism was present in the head of the sperm.
(vi) Those who considered homunculus to be present in ova (eggs) were called Ovist.
(vii) The term preformation covers the both.
(viii) Malpighi, Swammerdam & Bonnet believed that miniature organism was present in the egg.