Preformation


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Preformation

 

a biological theory, prevalent until the 18th century, according to which the sexual cells of an organism contain a fully formed embryo or parts of an embryo. Its supporters mistakenly rejected the idea that the parts of an embryo were formed during the embryo’s development.

J. Swammerdam, M. Malpighi, and A. Leeuwenhoek were among the first 17th-century microscopists who believed that the embryo was preformed. Ovists believed that preformation occurred in the ovum and animalculists believed it occurred in the sperm. The only changes that would occur during the organisms’ development would be an increase in size and a consolidation of its transparent, formerly invisible parts. In its extreme, preformation was based on creationism, or the dogma of the primordial creation of living beings that contained within themselves the rudiments of the embryos of all future generations. Opponents of spontaneous generation and other mechanistic theories of development, such as C. Bonnet, A. Haller, and L. Spallanzani, continued to substantiate preformation.

The concept that organisms develop as successive neoformations (epigenesis) gained prevalence in the second half of the 18th century. Preformation tended to be disproved by studies on sharp deviations from normal development, on the transmission of individual hereditary characteristics from both the mother as well as the father, and on the ability of the organism to regenerate.

The more primitive concept of preformation should be distinguished from preformism, which arose in the second half of the 19th century.

REFERENCES

Gaisinovich, A. E. K. F. Vol’fi uchenie o razvitii organizmov (V sviazi s obshchei evoliutsiei nauchnogo mirovozzreniia). Moscow, 1961.
Roger, J. Les Sciences de la vie dans la pensée française du XVIII siècle: La Generation des animaux de Descartes à l’Encyclopédie, 2nd ed. Paris, 1971.

A. E. GAISINOVICH

References in periodicals archive ?
Likewise, because Godwin rejects preformation as a kind of institution, one might see perfectibility as closer to epigenesis, which describes the progressive development of an embryo out of the amorphous flux of an egg cell, or in Godwin's Lockean terms, the emergence of the mind from its originary state as "an unfinished sketch" through a process of division and self-differentiation (PJ 1798, 1:36).
The fallacy of preformation, as if each and every Crusade-possibility were already in existence from the very beginning, denies the historical nature of the Crusades by removing the Crusades from the realm of history and transferring the Crusades to an original act of creation.
Preformation is generally the idea that the organism's form precedes its development, thereby involving a denial of the formative power of nature in respect to the organism.
Erasmus Darwin, grandfather of Charles and a proponent of preformation, held "that the embryon is produced by the male, and the proper food and nidus by the female.
Egg and Sperm and Preformation, The University of Chicago Press, 1997.
The paradigm shift from the idea of preformation to that of epigenesis produced a new ambiguity: while all people are now equipped with the triumphal knowledge that they will pass on a biological inheritance, this triumph is undermined by the insight that each of us is the product of a biological inheritance.
simple machine Time automatic machine Time 1 Thermal gluing of the 0,36 Thermal gluing of the 0,36 insertion in the sewing insertion in the sewing zone zone 2 Marking of the pocket 0,56 Positioning of the 0,18 position details 3 Application of the 2,4 Fixing the details and 0,35 insertion and preforming the pipe preformation of the pipe 4 Sewing the pocket 1,2 Sewing the pocket 0,40 5 Cutting the opening 1,3 Cutting the opening 0,18 Total 5,82 Total 1,47
His preformation theory of embryonic development survived in one form or the other until the 17th century.
Stone, Prebis, and others asserting that they mismanaged Thomas' medical condition and failed to diagnose abdominal abscesses, which resulted in preformation of his colon.
Otherwise, the partisans of the theory of preformation claim that every organism is completely predetermined in its germ.
This assumption, coupled with religious commitments, led to the competing theories of preformation and epigenesis.
SG refers to preformation three-year average growth rate of sales.