The word "preformation" is a noun that refers to the belief that all embryos contain miniature versions of themselves, rather than being created from scratch. The correct spelling of this word is /priːfɔːrˈmeɪʃən/. The first syllable is pronounced "pree," with a long "ee" sound. The second syllable is pronounced "for," with a short "o" sound. The third syllable is pronounced "may," with a long "a" sound, followed by "shun," with a "sh" sound and an unstressed "un" sound.
Preformation refers to a biological concept that originated in the 17th and 18th centuries, during the early development of embryology. It is the belief that all organisms, including humans, exist in miniature form within either the egg or the sperm before fertilization occurs. In other words, preformationists argued that the complete organism is already present in either the egg or the sperm cell, and the function of fertilization is merely to activate and unfold this preexisting structure.
This theory posits that organisms develop through a process of growth and expansion rather than the formation of new structures or organs. Proponents of this concept believed that the preformed structures, also known as "homunculi," contained all the information necessary to develop into a fully formed organism.
However, with advancements in cellular and developmental biology, preformation has largely been discredited. It was challenged by the concept of epigenesis, which suggests that organisms develop through a progressive process of cell differentiation and organ formation. Epigenesis has now become the widely accepted framework for understanding embryonic development.
The concept of preformation was significant historically as it contributed to debates on inheritance, genetics, and the role of both males and females in the development of offspring. Although it is no longer considered a valid explanation for embryonic development, preformation had a profound impact on the early scientific understanding of reproduction and development.
The doctrine that the entire organism exists in the germ (as a leaf in the bud) and that it is simply unfolded in the process of development.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "preformation" originates from the Latin roots "pre" meaning "before" and "formatio" meaning "formation". This term was coined in the 17th century to describe a theory in embryology which posited that all organs and structures of an organism exist fully formed in miniature within the germ cells before conception. The theory suggested that these preformed structures simply grow and unfold during development.