Recent molecular analyses reveal common themes in early
antero-posterior patterning in the four major groups of
invertebrate deuterostomes and vertebrates in spite of large
differences in the mode of gastrulation. Comparisons with
Drosophila and Cnidarians suggest a scheme for evolution of
the Bilaterian body plan and emphasize the pressing need for
similar studies in a wider variety of organisms, especially
more basal protostomes.