Haekel was professor of comparative anatomy at the University of Jena, where he worked for 47 years, from 1862 to 1909. Haekel discovered, described and named thousands of new species, mapped a tree of life relating all life forms. He coined many terms in biology, including "ecology", "phylum", "phylogeny", "stem cell", and the kingdom "Protista." Haeckel promoted and popularised Charles Darwin's work in Germany and developed the controversial recapitulation theory ("ontogeny recapitulates phylogeny"). This clained that an individual organism's biological development, or ontogeny, parallels and summarises its species' evolutionary development.