In November, 1853, Darwin received the Royal Society's Medal. He was gratified, finding it "a pleasant little stimulus. When work goes badly, and one ruminates that all is vanity, it is pleasant to have some tangible proof that others have thought something of one's labors." November 24, 1859, when Darwin was fifty, his great work, "Origin of Species by means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life," was published. For twenty years he had been making experiments with plants and animals, and filling his note-books with facts. To his old classmate, Fox, he writes asking that the boys in his school gather lizards' eggs, as well as those of snakes. "My object is," he says, "to see whether such eggs will float on sea-water, and whether they will keep alive thus floating for a month or two in my cellar. I am trying experiments on transportation of all organic beings that I can; and lizards are found on every island, and therefore I am very anxious to see whether their eggs stand sea-water." Again he writes, asking Fox for ducklings and dorkings; "The chief point which I am and have been for years very curious about is to ascertain whether the _young_ of our domestic breeds differ as much from each other as do their parents, and I have no faith in anything short of actual measurement and the Rule of Three.... I have got my fan-tails and pouters in a grand cage and pigeon-house, and they are a decided amusement to me, and delight to H." Of this book, Darwin himself says: "I worked on true Baconian principles, and without any theory--collected facts on a wholesale scale, more especially with respect to domesticated productions, by printed inquiries, by conversation with skilful breeders and gardeners, and by extensive reading. When I see the list of books of all kinds which I read and abstracted, including whole series of Journals and Transactions, I am surprised at my industry. I soon perceived that selection was the keystone of man's success in making useful races of animals and plants....