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📘 An Examination of Weismannism

You came for the loudest fight in 1893 biology: can a body's experience enter the next generation? George John Romanes dates his preface at Christ Church, Oxford, in July, and refuses to fight it. An Examination of Weismannism, issued that

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~25 min
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What you’ll learn

  1. A theory in two layersSee the 1893 book as a split: a theory of heredity versus an evolutionary system that needs two extra postulates, with the acquired-character question parked.Open Court, Chicago, 1893; preface, Christ Church, July. Weismann's Keimplasma is 1892; Parker's English is 1893. Hamlet is the next volume.
  2. Darwin against WeismannContrast pangenesis (centripetal gemmules) with germ-plasm (centrifugal stock), including the perennial-stem picture and the Begonia leaf that both theories can house.Seven Darwinian assumptions. Traffic, not whether heredity is material. A leaf that roots does not yet choose a theory.
  3. The two loaded wordsSeparate a high degree of hereditary stability from Weismann's perpetual continuity and absolute stability, and see what those adverbs would do to variation.Galton: barely, if at all. If both adverbs hold, Metazoan variation is only sexual mixture. Romanes thinks they do not hold.
  4. Compatible is not proofTreat hydromedusa migration, early germ-cell isolation, and parthenogenetic invariance as tests that fail to uniquely confirm total isolation.Migration fits stirp. Early isolation is not general and Weismann later dropped it. Parthenogenetic invariance is false as fact.
  5. The fair readingKeep Galton's modest continuity, refuse Spencer's telegony fork, and leave the body-germ question open on a plant you can grow from a leaf.Stirp already had the heredity theory. Telegony, if facts, does not uniquely wreck germ-plasm. Barely is not never.

Questions this course answers

What does Romanes treat as Weismann's two extra postulates, needed for the evolutionary system but not for a modest theory of heredity?

Summary and Chapter III: heredity needs continuity and a high degree of stability. The evolutionary superstructure needs continuity as perpetual 'since the first origin of life' and stability as absolute 'since the first origin of sexual reproduction.'

Match the 1893 label to the theory Romanes is actually comparing

Chapter I and III: pangenesis vs germ-plasm as logical extremes; stirp as the nearer neighbour; the preface parks the fact-question.

In what year was An Examination of Weismannism published?

Open Court, Chicago, 1893. Preface dated Christ Church, Oxford, July 1893. Weismann's German Keimplasma is 1892; Parker's English Germ-Plasm is also 1893.

How does pangenesis differ from germ-plasm in the direction of hereditary traffic?

Chapter III: taking the sexual elements as centre, germ-plasm originates there and travels centrifugally; pangenesis originates at the periphery and travels centripetally.

Why does Romanes spend so much time on Galton's stirp?

Stirp is continuous but not necessarily absolutely so, stable but not unalterably so. Romanes: Weismann's heredity theory is essentially Galton's; the extras belong to the evolutionary system.

What is Romanes's point about Weismann's hydromedusa germ-cell migration?

Chapter III: the migration is Weismann's own research and is not denied. It does not choose among theories that all need specialized germ-cells. These animals can also regenerate from body fragments.

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