The Riddle of the Universe (Barnes & Noble Digital Library)

Ernst Haeckel (1834-1919) was a German biologist and artist who championed Darwin's theory of evolution.  He was a proponent of the recapitulation theory, summarized in his pithy phrase "ontogeny recapitulates phylogeny"—i.e., the development of the individual reproduces in miniature that of the species as a whole.  Haeckel also discovered thousands of new species, coined many biological terms, and produced artwork of land and sea creatures.