Portrait of Ernst Heinrich Haeckel (1834 - 1919), the German biologist and Darwinist who coined the words 'ecology', 'ontogeny' and 'phylogeny'. After studying various marine invertebrates, Haeckel was the first to divide animals into unicellular (protozoan) and multicellular (metazoan) categories. Haeckel also proposed the theory that an embryo reveals the history of evolution as it develops and that prehistoric creatures resembled the embryos of modern animals. This 'evolutionary recapitulation' concept has since been proven incorrect. A major supporter of Darwin's theory of evolution, Haeckel used natural selection to justify the idea that Germans are a master race.