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Pangenesis was Charles Darwin's hypothetical mechanism for heredity. He presented this 'provisional hypothesis' in his 1868 work ''The Variation of Animals and Plants under Domestication'' and felt that it brought 'together a multitude of facts which are at present left disconnected by any efficient cause'. The etymology of the word comes from the Greek words ''pan'' (a prefix meaning "whole", "encompassing") and ''genesis'' ("birth") or ''genos'' ("origin"). The hypothesis was eventually replaced by Mendel's laws of inheritance. The pangenesis theory, similar to Hippocrates's views on the topic, imply that the whole of parental organisms participate in heredity (thus the prefix ''pan'') while adapting to cell theory. Much of Darwin's model was speculatively based on inheritance of tiny heredity particles he called gemmules that could be transmitted from parent to offspring. Darwin emphasized that only cells could regenerate new tissues or generate new organisms. He posited that atomic sized gemmules formed by cells would diffuse and aggregate in the reproductive organs. ==Early history== The hypothesis of pangenesis was developed by the ancient Greek philosophers such as Hippocrates and Democritus.〔Zirkle, Conway. (1935). ''The Inheritance of Acquired Characters and the Provisional Hypothesis of Pangenesis''. ''The American Naturalist'' 69: 417-445.〕 Darwin wrote that Hippocrates' pangenesis was "almost identical with mine—merely a change of terms—and an application of them to classes of facts necessarily unknown to the old philosopher."〔Deichmann, Ute. (2010). ''Darwinism, Philosophy, and Experimental Biology''. Springer. pp. 41-42. ISBN 978-90-481-9901-3〕 Historian of science Conway Zirkle has noted: The hypothesis of pangenesis is as old as the belief in the inheritance of acquired characters. It was endorsed by Hippocrates, Democritus, Galen (?), Clement of Alexandria, Lactantius, St. Isidore of Seville, Bartholomeus Anglicus, St. Albert the Great, St. Thomas of Aquinas, Peter of Crescentius (?), Paracelsus, Jerome Cardan, Levinus Lemnius, Venette, John Ray, Buffon, Bonnet, Maupertius, von Haller and Herbert Spencer.〔 A very similar hypothesis to Darwin's pangenesis was held by the French naturalist Georges-Louis Leclerc, Comte de Buffon who developed a system of heredity.〔Hull, David L. (1988). ''Science as a Process: An Evolutionary Account of the Social and Conceptual Development of Science''. University of Chicago Press. p. 86. ISBN 0-226-36051-2 "As Darwin was to discover many years later, Buffon had devised a system of heredity not all that different from his own theory of pangenesis."〕 Commenting on Buffon's views, Darwin stated, "If Buffon had assumed that his organic molecules had been formed by each separate unit throughout the body, his view and mine would have been very closely similar."〔 In 1801, Erasmus Darwin advocated a hypothesis of pangenesis in the third edition of his book ''Zoonomia''.〔Deichmann, Ute. (2010). ''Darwinism, Philosophy, and Experimental Biology''. Springer. p. 42. ISBN 978-90-481-9901-3 "Among the other authors were Buffon, who proposes "organic molecules" with affinities to various organs, and, in particular, Erasmus Darwin, who in 1801 anticipated his grandson's concept of pangenesis, suggesting that small particles were given off by parts of the bodies of both parents; and that they are circulated in the blood, ending in the sexual organs from where they could be combined during reproduction in order to form the nucleus of an offspring."〕 The Irish physician Henry Freke in his book ''Origin of Species by Means of Organic Affinity'' (1861) developed a variant of pangenesis.〔Macalister, Alexander. (1870). ''Reviews and Bibliographical Notices''. In ''Dublin Quarterly Journal of Medical Science, Volume 50''. Fannin and Company. p. 131〕 In 1864, Herbert Spencer in his book ''Principles of Biology'', proposed a theory of "physiological units". These hypothetical hereditary units were similar to Darwin's gemmules.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「pangenesis」の詳細全文を読む スポンサード リンク
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