Endless Forms Most Beautiful Chapter 2 by Greg Weiss

“For example, in the chicken wing bud, cells close to the ZPA developed the posterior type of digit 4 and those farther away progressively developed more anterior type of digits” (45).

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2024-03-08 15:36:11 UTC

“More interesting, he found that when this small group of cells was isolated from the developing butterfly wing in the first day of the chrysalis stage and transplanted to a site elsewhere on the wing, a new eyespot now appeared” (Chapter 2, 43-44).

2024-03-08 15:36:19 UTC

“When Spemann divided the egg differently by tying it perpendicular to the furrow between the two cells of the embryo, he obtained a dramatically different result. Only one side made a normal tadpole, while the other made a disorganized mess of belly tissue” (Ch 2, p 41).

24mclaughlinc2 — 2024-03-08 15:36:41 UTC

“When Spemann divided the egg differently by tying it perpendicular to the furrow between the two cells of the embryo, he ontained a dramatically different result. Only one side made a normal tadpole, while the other made a disorganized mess of belly tissue” (41, Ch. 2).

2024-03-08 15:36:53 UTC

“The fact that such variations arise does not mean that these are founders of new types or species. Rather, from what we now know these monsters are almost certainly misfits that will be swept away by the power of natural selection with no chance of passing on their traits"(46).

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"In Drosophila, only a small number of “homeotic” genes give homeotic forms when they are mutated, indicating that a small number of “master’ genes govern the differentiation of serially homologous body parts in the fly"

2024-03-08 15:37:36 UTC

"This tiny pad of tissue will grow outward, lengthen, and develop bone, cartilage, muscles, tendons, digits, and feathers in a beautiful display of the coordinated processes of development. Perhaps most striking is the orderly formation of cartilage elements…there must be some sort of system that cues cells as to what they will become." (pg 42)

2024-03-08 15:37:40 UTC

In Drosophila, only a small number of “homeotic” genes give homeotic forms when they are mutated, indicating that a small number of “master” genes govern the differentiation of serially homologous body parts in the fly.”(51)

"It is remarkable how these homeotic mutants can so completely transform one structure into another"(50)

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24tuckerhillc2 — 2024-03-08 15:40:57 UTC

“It did turn out that Bateson’s kinds of monsters were informative, not so much for telling us about the true cause of evolution, but for insights into development that bear on evolution… Bateson’s monsters were “helpful” scientifically, but hopeless as individuals.” (Chapter 2, page 48)