Deep homology
In evolutionary developmental biology, the concept of deep homology is used to describe cases where growth and differentiation processes are governed by genetic mechanisms that are homologous and deeply conserved across a wide range of species. == History == In 1822, the French zoologist Étienne Geoffroy Saint-Hilaire dissected a crayfish, discovering that its body is organised like a vertebrate's, but inverted belly to back (dorsoventrally): I just found that all the soft organs, that is to say, the principal organs of life are found in crustaceans, and so in insects, in the same order, in the same relationships and with the same arrangement as their analogues in the high vertebrate animals ...