In the special branch of study which Wallace himself set going--the inquiry into the local variations, races, and species of insects as evidence of descent with modification, and of the mechanism by which that modification is brought about--there is still great work in progress, still an abundant field to be reaped.... Several able observers and experimenters have set themselves the task of improving, if possible, the theoretical structure raised by Darwin and Wallace.... But I venture to express the opinion that they have none of them resulted in any serious modification of the great doctrine submitted to the Linnean Society on July 1st, 1858, by Charles Darwin and Alfred Russel Wallace. Not only do the main lines of the theory of Darwin and Wallace remain unchanged, but the more it is challenged by new suggestions and new hypotheses the more brilliantly do the novelty, the importance, and the permanent value of the work by those great men, to-day commemorated by us, shine forth as the one great epoch-making effort of human thought on this subject. Sir Francis Darwin and Sir William Thiselton-Dyer spoke on behalf of Schools which had sent representatives to the meeting; Prof. Lönnberg and Sir Archibald Geikie on behalf of the Academies and Societies; while Lord Avebury delivered the concluding address. Any summary of this period in the lives of Darwin and Wallace would be incomplete without some distinct reference to one other name, namely, that of Herbert Spencer, whom I have linked with them in the Introduction. While we owe to Darwin and Wallace a definite theory of organic development, it must be remembered that Spencer included this in the general scheme of Evolution which grew as slowly but surely in his mind--and as independently as did that of the origin of species in the minds of Darwin and Wallace. Huxley recalls: "Within the ranks of biologists, at that time, I met with nobody except Dr. Grant, of University College, who had a word to say for Evolution--and his advocacy was not calculated to advance the cause. Outside these ranks, the only person known to me whose knowledge and capacity compelled respect, and who was, at the same time, a thorough-going evolutionist, was Mr. Herbert Spencer.... Many and prolonged were the battles we fought on this topic.... I took my stand upon two grounds: first, that up to that time the evidence in favour of transmutation was wholly insufficient; and, secondly, that no suggestions respecting the causes of the transmutations assumed ... were in any war adequate to explain the phenomena. Looking back at the state of knowledge at that time, I really do not see that any other conclusion was justifiable."[25]