Darwin's octopus, Spirit Rooms, Natural History Museum, London (2019). The museum had a vast collection of specimens assembled since the nineteenth century. This, a preserved octopus, was collected by Charles Darwin. In his journals, which eventually became the book "Voyage of the Beagle", Darwin records his excitement at seeing an octopus change colour, and wrote back to his teacher, Henslow, in Cambridge, that he thought he had made a "discovery". Henslow, very tactfully, wrote back to tell Darwin that the ability of octopuses to change colour had been known for an extremely long time. Undaunted by this setback, the young Darwin went on to make a few more "discoveries".