is the birthday of Ernst Haeckel, a German zoologist and evolutionist born in 1834 who was a proponent and popularizer of Darwinian evolution.
Haeckel studied the one-celled protozoan group Radiolaria and noticed they often have crystalline structures in their cells, leading him to propose--incorrectly--that the earliest life-forms arose by a sort of crystallization from inorganic matter. But he speculated correctly, as early as 1866, that the cell nucleus was concerned with inheritance.
After reading Darwin's theories, Haeckel lectured on evolution to scientific and lay audiences for years. He set forth, in popular writings, his own idea that evolution provided a unified explanation for all of nature, and drew up a human ancestral tree to show man's descent from other animals. Haeckel died in 1919.
[Source: Britannica Online]