preformation

noun

pre·​for·​ma·​tion ˌprē-fȯr-ˈmā-shən 

1

: previous formation

2

: the now discredited theory that every germ cell contains the organism of its kind fully formed and that development involves merely an increase in size compare epigenesis sense 1, homunculus sense 2

preformationist

ˌprē-fȯr-ˈmā-sh(ə-)nist 

noun or adjective

Word History

First Known Use

1732, in the meaning defined at sense 1

Medical Definition

preformation

noun

pre·​for·​ma·​tion ˌprē-fȯr-ˈmā-shən 

: a now discredited theory in biology that every germ cell contains the organism of its kind fully formed and complete in all its parts and that development involves merely an increase in size from microscopic proportions to those of the adult compare epigenesis

preformationist

-shə-nəst 

noun or adjective