Fifty years ago, coinciding with the centennial of the release of Darwin’s manuscript, author Morse Peckham collected all six editions into a single “variorum” text. Peckham painstakingly created a reference system that denotes the modifications and changes between editions. The text was created by Peckham’s careful enumeration of every sentence from every edition, copied onto index cards; from these cards, he carefully assembled them into a final text.