preformation

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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.
Farlex Partner Medical Dictionary © Farlex 2012

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.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

preformation

(prē-fawr-mā′shŭn)
In embryology, the development of structures from pre-existing templates, e.g., of bones from cartilage templates.
Medical Dictionary, © 2009 Farlex and Partners
References in periodicals archive ?
Just as modern, gene-oriented views of reproduction derive from preformation doctrine, modern regulation of abortion derives from a preformationist understanding of the embryo as an essentially complete new being.
Reva Siegel's foundational work on abortion restrictions in the United States highlights the preformationist views on which the nineteenth-century anti-abortion movement was based.
"(112) A zygote is "internally activated"--i.e., the genetic blueprint itself, rather than the gestational process, triggers development--and the genome itself "assumes control of the whole morphogenetic process from the beginning of embryonic development." (113) These claims are radically preformationist. According to Lugosi, the zygote proceeds to "execute a plan" that is best carried out "[u]ndisturbed by external intervention....
Moreover, the preformationist framing of the debate sets the terms of discussion even for those who accept Roe's terminology of "potential life." The prevailing legal analysis of artificial wombs, including among those who support the right to abortion today, is that they will eliminate both the need and the justification for abortion rights.