Darwin went public with his views on human evolution in The Descent of Man, and Selection in Relation to Sex (1871) and The Expression of the Emotions in Man and Animals (1872). By that time, he had been researching the subject on and off for decades, sometimes in unexpected directions. While on the Beagle, for example, he had met a surgeon who reported that the lice infesting Sandwich Islanders on his whaling ship were very distinctive and, furthermore, that when these lice crawled onto white men, the lice soon died. Darwin made a note about the story, adding: “If these facts were verified their interest would be great. – Man springing from one stock according his varieties having different parasites” (CUL DAR 31.315). That was in 1834, before Darwin believed that species evolve. He was nevertheless wondering how to connect the fact (as it seemed) that the human races, originating from a single stock, formed mere varieties within a single species, with the fact (as it seemed) that those races were so different physiologically as to sustain different species of lice. In 1844, and again in 1865, he quizzed England’s leading louse expert, Henry Denny, about it all – in the interim attempting to get Denny some lice from American blacks. In the Descent, Darwin cited Denny in a paragraph-long discussion of the matter. On the whole, Darwin judged, the facts about lice – and the surgeon’s observations had since been confirmed more generally – seemed to support the ranking of the different human races as distinct species (Darwin 1871a, 1:219–20; Radick and Steadman forthcoming).