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 ?
(80) To make things even more puzzling, Kant had sought initially to make the connection between his transcendental philosophy and preformationism, rather than with epigenesis, in order to make the case that the a priori categories were pre-given in the understanding, but revised it in the 1787 version of the first Critique.
Asi como desde el mismo autor el ya citado Leibniz's preformationism: Between metaphysics and biology>>, Analecta Husserliana, 2002, Vol.
Preformationism was also a theory of biological development.
In addition to its breathtaking simplicity, writes Pinto-Correia, preformationism offered an implicit rationale for the European caste system (kings are born from kings, peasants from peasants).
The primary argument considered here is preformationism (divine predetermination of life) vs.
(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.
According to Kullmann, by a strange irony of history, Aristotle's objections against Democritus are still valid against Darwin's (hypothesis of) preformationism; see Aristoteles, 31 and 311.
It is argued that Kant's theory of the categories was initially grounded on a contemporary version of "germ preformationism" involving a concept of preformed Keime that worked in company with natural Anlagen to bring about the synthesis of a priori and experience.