Ernst Haeckel's Bats (1904) – The Public Domain Review
Ernst Haeckel in the history of biology - ScienceDirect
Ernst Haeckel: the art of evolution – in pictures | Books | The Guardian
Ernst Haeckel (1834-1919) 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