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 ?
(78) On the other hand, while for most of his career, Kant had been a preformationist, following from the work of Caspar Friedrich Wolff's (1733-1794) Theoria Generationis (1759) and Johan Friedrich Blumenbach's (1752-1840) Institutiones Physiologicae (1787), Kant only gradually came to articulate the superiority of the theory of epigenesis over that of preformation. In the Critique of the Power of Judgment, he attempts to provide evidence that supports the former, (79) but it must be noted that Kant's defense of epigenesis was of a considerably weak form, when compared with Herder's, and later Schelling's versions of the theory.
Consequently, Godwin also draws a suggestive comparison between institution and biological theories of preformation, which claim there is a "mystical magazine, shut up in the human embryo, whose treasures are to be gradually unfolded" (PJ 1798, 1:31).
For more on preformation theory see Needham (note 21), 163, 168-70, 175, 205-11.
After all, preformation does play a role in reproduction; what is preformed is not the fetus per se but the instructions for making a fetus, DNA.
Extreme preformation in an alpine Polygonum viviparum: an architectural and developmental analysis.
1990), and organ preformation is widespread among angiosperms (Geber et al.
Focusing on one of the above five information formation periods (i.e., preformation, information, transformation, uniformation, and reformation/conformation/deformation); and
This tension was inherited from the neo-Kantians: already Cassirer's work, Richardson argues, was marred by the inability to decide between the conception of the synthetic a priori as the relative conventionalist a priori determinations that allow for the formulation of various theories and that of the synthetic a priori as a preformation of any rational thought.
--, 1971, "Preformation and Pre-existence in the 17th Century", Journal of the History of Biology, vol.
Each in turn examined the theory of preformation in the light of natural philosophy and religion.
The cord construction design parameters, such as the number of filaments, the filament diameters, lay lengths and directions, as well as the preformation type and degree are important to determine the cord geometry for good rubber penetration.
SG refers to preformation three-year average growth rate of sales.