August Weismann
August Friedrich Leopold Weismann (17 January 18345 November 1914) was a German evolutionary biologist. Fellow German Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg.His main contribution involved germ plasm theory, at one time also known as Weismannism, according to which inheritance (in a multicellular animal) only takes place by means of the germ cells—the gametes such as egg cells and sperm cells. Other cells of the body—somatic cells—do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. Biologists refer to this concept as the Weismann barrier. This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck. However, a careful reading of Weismann's work over the span of his entire career shows that he had more nuanced views, insisting, like Darwin, that a variable environment was necessary to cause variation in the hereditary material.
The idea of the Weismann barrier is central to the modern synthesis of the early 20th century, though scholars do not express it today in the same terms. In Weismann's opinion the largely random process of mutation, which must occur in the gametes (or stem cells that make them) is the only source of change for natural selection to work on. Weismann became one of the first biologists to deny Lamarckism entirely. Weismann's ideas preceded the rediscovery of Gregor Mendel's work, and though Weismann was cagey about accepting Mendelism, younger workers soon made the connection.
Weismann is much admired today. Ernst Mayr judged him to be the most important evolutionary thinker between Darwin and the evolutionary synthesis around 1930–1940, and "one of the great biologists of all time". Provided by Wikipedia
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81
Ueber die Hypothese einer Vererbung von Verletzungen Vortrag, gehalten am 20. September 1888 auf der Naturforscher-Versammlung zu Köln by Weismann, August, 1834-1914
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82
Das Keimplasma eine Theorie der Vererbung by Weismann, August, 1834-1914
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83
Neue Gedanken zur Vererbungsfrage eine Antwort an Herbert Spencer by Weismann, August, 1834-1914
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84
Ueber die Ewigkeit des Lebens by Weismann, August, 1834-1914
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85
[Über das Problem der Vererbung] by Weismann, August, 1834-1914
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86
Ueber den Ursprung der Hippursaeure im Harn der Pflanzenfresser Eine von der medicinischen Facultaet der Georgia Augusta am 13. Juni 1857 gekrönte Preisschrift by Weismann, August, 1834-1914
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87
Über die Vererbung ein Vortrag by Weismann, August, 1834-1914
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88
Über Bau und Lebenserscheinungen von Leptodora hyalina by Weismann, August 1834-1914
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89
Über einige neue oder unvollkommen gekannte Daphniden by Gruber, August, Weismann, August
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90
<<Die>> Entwicklung der Dipteren ein Beitrag zur Entwicklungsgeschichte der Insecten by Weismann, August 1834-1914
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91
Vorträge über Descendenztheorie gehalten an der Universität zu Freiburg im Breisgau by Weismann, August 1834-1914
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92
Vorträge über Descendenztheorie gehalten an der Universität zu Freiburg im Breisgau by Weismann, August 1834-1914
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93
Vorträge über Descendenztheorie gehalten an der Universität zu Freiburg im Breisgau by Weismann, August 1834-1914
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<<Die>> Bedeutung der sexuellen Fortpflanzung für die Selektions-Theorie by Weismann, August 1834-1914
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Über Leben und Tod eine biologische Untersuchung by Weismann, August 1834-1914
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96
Vorträge über Descendenztheorie gehalten an der Universität zu Freiburg im Breisgau by Weismann, August 1834-1914
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<<Das>> Keimplasma eine Theorie der Vererbung by Weismann, August 1834-1914
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98
Das Thierleben im Bodensee by Weismann, August 1834-1914
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99
Äussere Einflüsse als Entwicklungsreize. by Weismann, August, 1834-1914
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100
Ueber die Vererbung / by Weismann, August, 1834-1914
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