Both of these branches of evolutionary science, are, in my opinion, in the closest causal connection; this arises from the reciprocal action of the laws of heredity and adaptation.

Haeckel believed privately that his figures were both exact and synthetic and in public asserted that they were schematic like most figures used in teaching. Rather than being a strict Darwinian Haeckel believed that racial characteristics were acquired through interactions with the environment and that ontogeny directly followed phylogeny. As a book for the general public it followed the common practice of not citing sources.

The publiErnst Haeckeld artwork of Haeckel includes over 100 detailed multi-colour illustrations of animals and sea creatures (see: Kunstformen der Natur "Art Forms of Nature"). Haeckel promoted and popularized Charles Darwin's work in Germany and developed the controversial recapitulation theory ("ontogeny recapitulates phylogeny") claiming that an individual organism's biological development or ontogeny parallels and summarizes its species' evolutionary development or phylogeny. Ernst Heinrich Philipp August Haeckel (February 16 1834 – August 9 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 the kingdom Protista.