Sir Joseph Hooker and Professor Huxley were among the first to give in their adhesion and stand up boldly for the new truth by the side of the reckless and disturbing innovator. In June 1859, nearly a year after the reading of the Darwin-Wallace papers at the Linnean Society, but five months previously to the publication of the 'Origin of Species,' Huxley lectured at the Royal Institution on 'Persistent Types of Animal Life,' and declared against the old barren theory of successive creations, in favour of the new and fruitful hypothesis of gradual modification. In December 1859, a month later than the appearance of Darwin's book, Hooker published his 'Introduction to the Flora of Australia,' in the first part of which he championed the belief in the descent and modification of species, and enforced his views by many original observations drawn from the domain of botanical science. For fifteen years, as Darwin himself gratefully observed in his introduction to the 'Origin of Species,' that learned botanist had shared the secret of natural selection, and aided its author in every possible way by his large stores of knowledge and his excellent judgment. Bates, the naturalist on the Amazons, followed fast with his beautiful and striking theory of mimicry, a crucial instance well explained. The facts of the strange disguises which birds and insects often assume had long been present to his acute mind, and he hailed with delight the discovery of the new principle, which at once enabled him to reduce them with ease to symmetry and order. To Herbert Spencer, an evolutionist in fibre from the very beginning, the fresh doctrine of natural selection came like a powerful ally and an unexpected assistant in deciphering the deep fundamental problems on which he was at that moment actually engaged; and in his 'Principles of Biology,' even then in contemplation, he at once adopted and utilised the new truth with all the keen and vigorous insight of his profound analytic and synthetic intellect. The first part of that important work was issued to subscribers just three years after the original appearance of the 'Origin of Species;' the first volume was fully completed in October 1864. It is to Mr. Spencer that we owe the pellucid expression 'survival of the fittest,' which conveys even better than Darwin's own phrase, 'natural selection,' the essential element added by the 'Origin of Species' to the pre-existing evolutionary conception.