Ernst Heinrich Philipp August Haeckel (February 16, 1834 - August 8, 1919) was a German biologist and philosopher who popularized Charles Darwin's work in Germany. Haeckel was a physician and later a professor of comparative anatomy. He was one of the first to consider psychology as a branch of physiology. He also proposed many now ubiquitous terms including "phylum" and "ecology." His chief interests lay in evolution and life development processes in general, including development of nonrandom form, which culminated in the beautifully illustrated Kunstformen der Natur (Art forms of nature).
Haeckel's observations on the link between ontogeny (development of form) and phylogeny (evolutionary descent) have been named the "recapitulation theory", summed up in the phrase, "ontogeny recapitulates phylogeny". Haeckel's efforts to prove this hypothesis were probably misguided and inaccurate.
Haeckel was also known for his "biogenic theory ", in which he suggested that the development of races paralleled the development of individuals. He advocated the idea that "primitive" races were in their infancies and needed the "supervision" and "protection" of more "mature" societies.
Haeckel was a flamboyant figure whose popularity with the public was substantially greater than it was with his scientific peers. Although Haeckel's ideas are important to the history of evolutionary theory, and he was a competent invertebrate anatomist most famous for his work on radiolaria, most of the speculative concepts that he championed are now seen as incorrect. For example, Haeckel described and named hypothetical ancestral micro-organisms that have not been found and almost certainly did not exist. His concept of recapitulation has been disproven. Haeckel did not support Darwin's "survival of the fittest", rather believing in a Lamarckian inheritance of acquired characteristics. On top of picking several wrong concepts to champion, he was actually caught using doctored data in some of his papers. Most notably his drawings of embryos were known, even by contemporaries, to deliberately misrepresent the similarities between embryos of different species.