After completing his studies in medicine and biology, a restless Ernst Haeckel set off for Italy in 1859 to study art and marine biology. The diversity of life fascinated the 26-year-old Prussian, and in addition to painting landscapes, he spent the climactic months of his stay glued to his microscope observing and sketching radiolaria—protozoa encased in delicately ornate silica skeletons—that he collected off the Italian coast and sent back to Berlin. He was amazed by the diversity of their forms, which seemed to come in limitless, but sortable, varieties, and on returning from Italy set to work cataloging them. During this time of youthful soul-searching and vocation-finding, Haeckel stumbled upon a German translation of the recently published Origin of Species and experienced one of the most momentous revelations of his career.
In the fourth chapter of Charles Darwin’s treatise was a drawing that illustrated the evolution of a single hypothetical ...
