Darwin's theory was arrived at from data taken from the biological realm, and consists of two doctrines. One is the doctrine of =natural selection=, which was his own personal contribution to the discussion, and the other is that of =the inheritance of acquired characters=, which he borrowed from Lamarck. The former is the doctrine meant when pure Darwinism is referred to. (i). The Doctrine of Natural Selection. Darwin himself said: We cannot prove that a single species has changed, and, also, Many of the objections to the hypothesis of evolution are so serious I can hardly reflect on them without being staggered. Dr. N. S. Shaler, department of geology, Harvard, says: It begins to be evident that the Darwinian hypothesis is still essentially unverified.... It is not yet proven that a single species of the two or three million now inhabiting the earth had been established solely or mainly by the operation of natural selection. Professor Fleischmann, of Erlangen, has said: The Darwinian theory of descent has in the realms of nature not a single fact to confirm it. It is not the result of scientific research, but purely the product of the imagination. And John Burroughs, although an evolutionist up to his recent death, said of Darwin, in the August, 1920, "Atlantic Monthly": He has already been as completely shorn of his selection doctrines as Samson was shorn of his locks. If these statements from scientific men mean anything at all, they mean, at least, that pure Darwinism is altogether unproven, if not that it is dead. (ii). The Doctrine of Acquired Characters. Spencer made this doctrine the fundamental one in his evolutionary philosophy. Its importance was so vital to him that he said: Close contemplation of the facts impresses me more strongly than ever with the two alternatives--either there has been inheritance of acquired characters, or there has been no evolution. It is of great interest, therefore, to note what competent scientists have said about this doctrine. Dr. Thomas Hunt Morgan, department of science, Columbia University, says: Today the theory has few followers among trained investigators, but it still has a popular vogue that is wide-spread and vociferous. Alfred Russell Wallace, in his "Autobiography," said: All the available evidence is opposed to the doctrine of acquired characters. Prof. William Bateson, in his 1914 Presidential Address before the British Association for the Advancement of Science, said: We have done with the notion that Darwin came latterly to favor, that large differences can arise by the accumulation of small differences. He also remarks that the new knowledge of heredity shows that whatever evolution there is occurs by loss of factors and not by gain, and that in this way the progress of science is destroying much that till lately passed for gospel.