In France, Étienne Geoffroy Saint-Hilaire attempted to portray the skeleton of vertebrates as a set of modifications upon an archetypal vertebra. In the 1820's, Geoffroy extended his ambitious plan to include annelids and arthropods under that same rubric.... Vertebrates support their soft parts with an internal skeleton, but insects must live within their vertebrae (a reality, not a metaphor, for Geoffroy). This comparison led to... the claim that a vertebrate rib must represent the same organ as an arthropod leg - and that insects must therefore walk on their own ribs!

"Brotherhood by Inversion", p. 326 - Leonardo's Mountain of Clams and the Diet of Worms (1998)