Ernst Heinrich Philipp August Haeckel (; 16 February 1834 – 9 August 1919) was a German
biologist,
naturalist, philosopher, physician, professor, and artist who discovered, described and named thousands of new
species, mapped a
genealogical tree relating all life forms, and coined many terms in
biology, including
anthropogeny,
ecology,
phylum,
phylogeny,
stem cell, and
Protista. Haeckel promoted and popularised
Charles Darwin's work in Germany and developed the influential but no longer widely held
recapitulation theory ("ontogeny recapitulates phylogeny") claiming that an individual organism's biological development, or
ontogeny, parallels and summarises its species' evolutionary development, or
phylogeny.