This plain consideration seems to account for a fact which is undoubtedly highly significant. Professor Huxley had certainly no prejudices against evolutionary systems, could they but be satisfactorily established. He knew all that Professor Haeckel has urged on behalf of his own theory, and showed how much he was in sympathy with it by naming after his friend the ill-starred _Bathybius Haeckelii_, the deep-sea slime which was at first supposed to bridge the gulf between the organic and the inorganic worlds, and to be living stuff in process of spontaneous manufacture. Nothing, in fact, as he himself admitted, in his controversy with Dr. Bastian, could have suited him better than a demonstration that Nature possesses all the powers necessary for her own processes, and that the explanation of all is within the scope of Science. But, at the same time, he reverenced scientific truth beyond anything else, and he was keenly sensible of the danger attending the use of hypothetical explanations, leading to conclusions which cannot be experimentally tested, which danger he carefully shunned.[32] Accordingly, not only did he never lend his countenance to what Professor Haeckel represents as the inevitable conclusions of Science, but he even plainly intimated that those who advanced such views were going much farther than Science warrants. The doctrine of Evolution, he declared,[33] is not only attacked on false grounds by its enemies, but is made by some of its friends to cover so much which is disputable, as to force him in self-defence to make his own position clear in its regard. And the first point of his explanation is to repudiate the idea that we have any such knowledge as Professor Haeckel assumes. "I have nothing to say," he writes, "to any 'Philosophy of Evolution.'" Being thus necessarily destitute of support either directly from observation or by inference from observed facts, it would seem that only in one way can Professor Haeckel's system of cosmogony, or world-production, obtain any support from Science. If amongst the operations now in progress in the universe, is to be found evidence of an exhaustless and self-renewing energy, a mainspring capable of keeping the machine going everlastingly, then undoubtedly there will be an explanation forthcoming, which, whatever difficulties may still remain on other grounds, will at least furnish a complete mechanical account of things within the ken of Science. May we not suppose that this is what is claimed as being supplied by the "Law of Substance," which is represented as the cornerstone of the whole edifice, the supreme triumph of scientific discovery, and, in fine, "the universal law of evolution"? Let us see how far such a notion can be styled scientific.