 Gould laid to rest Haeckel's interpretation of evolutionary embryology, while Jacob set out an alternative theory.This led to a second synthesis, at last including embryology as well as molecular genetics, phylogeny, and evolutionary biology to form evo-devo.In 1978, Edward B. Lewis discovered homeotic genes that regulate embryonic development in "Drosophila" fruit flies, which like all insects are arthropods, one of the major phyla of invertebrate animals.