This passage is quoted in the “Life and Letters” (Vol. III., p. 84), and Francis Darwin makes the convincing reply:-- “But my father’s parallel demands that natural selection shall be the architect, not the edifice--the question of design only comes in with regard to the form of the building materials.” Darwin’s reply was contained in his letter to Asa Gray dated May 8th, 1868:-- “You give a good slap at my concluding metaphor: undoubtedly I ought to have brought in and contrasted natural and artificial selection; but it seemed so obvious to me that natural selection depended on contingencies even more complex than those which must have determined the shape of each fragment at the base of my precipice. What I wanted to show was that, in reference to pre-ordainment, whatever holds good in the formation of an English pouter-pigeon holds good in the formation of a natural species of pigeon. I cannot see that this is false. If the right variations occurred, and no others, natural selection would be superfluous.” To this, Asa Gray replied in his letter of May 25th:-- “As to close of my article, to match close of your book,--you see plainly I was put on the defence by your reference to an old hazardous remark of mine. I found your stone-house argument unanswerable in substance (for the notion of design must after all rest mostly on faith, and on accumulation of adaptations, &c.); so all I could do was to find a vulnerable spot in the shaping of it, fire my little shot, and run away in the smoke. “Of course I understand your argument perfectly, and feel the might of it.” From this last letter I think we may conclude that Asa Gray’s feelings on this subject rested, as he says, “on faith,” and that, intellectually, he saw no way of meeting Darwin’s arguments. CHAPTER XVIII. INFLUENCE OF DARWIN UPON HUXLEY. [Sidenote: HUXLEY AND NATURAL SELECTION.] It is of the utmost interest to trace the influence of Darwin upon Huxley, his great General in the numerous controversial battles which had to be fought before the new views were to secure a fair hearing and, at length, complete success. Now that we are quietly enjoying the fruit of his many victories, we are apt to forget how much we owe to Huxley, not only for evolution, but for that perfect freedom in the expression of thought and opinion which we enjoy. For Huxley fought on wider issues than those raised by evolution, wide as these are; and with a success so great that it is inconceivable that any new and equally illuminating thought which the future may hold in store for us, will meet with a reception like that accorded to the “Origin of Species.”