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Generations of biology students may have been misled by a famous set of drawings of embryos published 123 years ago by the German biologist Ernst Haeckel. They show vertebrate embryos of different animals passing through identical stages of development. But the impression they give, that the embryos are exactly alike, is wrong, says Michael Richardson, an embryologist at St. George's Hospital Medical School in London. He hopes once and for all to discredit Haeckel's work, first found to be flawed more than a century ago.
Richardson had long held doubts about Haeckel's drawings because they didn't square with his understanding of the rates at which fish, reptiles, birds, and mammals develop their distinctive features. So he and his colleagues did their own comparative study, reexamining and photographing embryos roughly matched by spe cies and...