In recent years, evidence has accumulated that the insect ventral body side equals the dorsal side of the vertebrates and that chordates, during their evolution, have inverted their dorsoventral body axis (Arendt and Nübler-Jung, 1994, 1997; Holley et al., 1995; De Robertis and Sasai, 1996). In insects and vertebrates, the equivalent ‘neural’ body sides give rise to a prominent brain and nerve ...