As early as 1822, the French zoologist Étienne Geoffroy Saint-Hilaire noted that the organization of dorsal and ventral structures in arthropods is opposite that of mammals. … 展开

In addition to the simple observation that the dorsoventral axes of protostomes and chordates appear to be inverted with respect to each other, molecular biology provides some support for … 展开

• An explanation of DV patterning in Drosophila
• P.Z. Myers on axis inversion and hemichordates
• P.Z. Myers on axis inversion and annelids: "We have the brains of worms" 展开

While the idea of dorsoventral axis inversion appears to be supported by morphological and molecular data, others have proposed alternative plausible hypotheses (reviewed in … 展开