From the front matter of The Harvard Classics, Vol.22. "Essays English and American." Charles Eliot Norton, editor, emerges this image of the naturalist.
What a pose. Hamlet with the skull of Yorick, he is not. His skull is a mere object of study, held as any object would be, the hand in pocket pose making sure that no idea of reverence or even awe would be welcomed by the man whose gaze confronts us with intelligence and a hint of amusement, I fancy.