preformation

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Related to Preformationism: Germ-Plasm Theory

pre·for·ma·tion the·o·ry

archaic theory that the embryo was fully formed in miniature within a gamete at the time of conception.
See also: homunculus. Compare: epigenesis.

preformation

(prē′fôr-mā′shən)
n.
1. The act of shaping or forming in advance; prior formation.
2. A theory popular in the 1700s that all parts of an organism exist completely formed in the germ cell and develop only by increasing in size.

preformation

[-fôrmā′shən]
Etymology: L, prae + formatio, formation
an early theory in embryology in which the organism is contained in minute and complete form within the germ cell and after fertilization grows from microscopic to normal size. Compare epigenesis.

preformation

(prē-fawr-mā′shŭn)
In embryology, the development of structures from pre-existing templates, e.g., of bones from cartilage templates.
References in periodicals archive ?
69) Bard (2008) accounts for the origin of the word epigenetics as follows: "Epigenetics is actually a portmanteau term and a conflation of epigenesis--the belief that development is the gradual process of taking a simple egg and allowing complexity to develop (contrasting with preformationism, the idea that development is just the expansion of structures already present in the fertilized egg)--and genetics, the study of the laws of heredity" ('Waddinton's Legacy to Developmental Theoretical Biology,' Biological Theory, vol.
This is a principle which the materialisms, pangenesis and preformationism, do not comprehend.
23) His mention of it at this point (722b5), however, permits us to note that preformationism had been employed in Greek cultural life to deny women any role in generation, and consequently to deny them any significant connection with their children and any connection of their children with them.
Aristotle's opposition to preformationism is not founded on the grounds that it demeans women's part in generation.