Some interesting facts about Darwin were told yesterday in one of the Philosophy courses, as showing how an observance of economic laws often lead to the discovery of natural laws as well as vice versa. When Darwin was just beginning to develop his theory of species he received a letter from Wallace, who was then in the Greek Archipelago. Wallace told him (accompanying this letter was an essay, which Wallace told him contained a new theory on which he [Wallace] wrote) that as the essay was one which contained a new theory on which his thoughts had of late been running, he asked Darwin's advice as to its publication. Mr. Wallace confessed that he had been led to his opinions by a study of Malthus' "Doctrine of Population." Curiously enough, this theory was exactly the train of thought which Darwin himself had just been considering. He immediately took it to a great friend, a well-known historian, and told him of the strange coincidence. The friend advised him if there were any documents in proof of his own line of work at the time to publish them instantly. After much reflection and the conclusion that there were none to bring forward, Darwin suddenly remembered that he had once written a letter to Dr. Asa Gray, the famous botanist, of Cambridge, Mass., in which he had expressed the same views that Wallace had announced in his essay. The publication of this letter instantly set Mr. Darwin's claim to the equal right of the authorship of the "Doctrine of the Origin of Species" on a firm basis. And, most strange of all, in the "Life and Letters of Mr. Darwin" now in press, he declares that it was Malthus' Doctrine of Population" which first suggested the theory to his mind also.