Charles Darwin to John Stevens Henslow (18-May-1832):
St Jago [modern-day Porto Praya in the Cape Verde Islands] is singularly barren & produces few plants or insects.—so that my hammer was my usual companion, & in its company most delightful hours I spent.—
On the coast I collected many marine animals chiefly gasteropodous (I think some new).— I examined pretty accurately a Caryophyllea & if my eyes were not bewitched former descriptions have not the slightest resemblance to the animal.— I took several specimens of an Octopus, which possessed a most marvellous power of changing its colours; equalling any chamaelion, & evidently accommodating the changes to the colour of the ground which it passed over.—yellowish green, dark brown & red were the prevailing colours: this fact appears to be new, as far as I can find out.
Darwin was hopelessly wrong about the colour-changing ability of octopuses being a new observation. But never mind: the good news is that one of Darwin's St Jago octopuses is still alive and kicking preserved for posterity in Cambridge, and I have photos to prove it:
Darwin's octopus
The accompanying label