The biologist cannot fail to be impressed by the fact that his science to-day is, roughly and broadly speaking, in the position which Chemistry and Physics occupied a century ago. It is beginning to reach down from observation to experimental analysis, and from experimental analysis to grasp of principle. Furthermore, as the grasp of principles in physico-chemical science led speedily to an immense new extension both of knowledge and of control, so it is not to be doubted that like effects will spring from like causes in biology. But whereas the extension of control in physics and chemistry led to a multiplication of the number of things which man could do and experience, the extension of control in biology will _inter alia_ mean an alteration of the modes of man’s experience itself. The one, that is to say, remained in essence a quantitative change so far as concerns the real life of man; the other can be a qualitative change. Applied physics and chemistry bring more grist to the mill; applied biology will also be capable of changing the mill itself. The possibilities of physiological improvement, of the better combination of existing psychical faculties, of the education of old faculties to new heights, and of the discovery of new faculties altogether--all this is no utopian silliness, but is bound to come about if science continues her current progress. Take but one example. In the first half of last century, hypnotism, or mesmerism as it was then called, was in complete scientific disrepute. To-day, all the main claims of its founders have been verified, and many new facts unearthed. Every text-book on the subject will tell you that men may be made insensible to pain by hypnosis alone without any drug, many women even being delivered of children under its influence without suffering. Temperature can be changed, blisters raised, and many other processes not normally under the control of the will can similarly be affected. The mind can be raised to an abnormal sensitiveness, in which differences between objects that are completely unrecognizable in ordinary waking existence, such as those between the backs of two cards in a pack, may be easily distinguished. If such possibilities are open to the empiricism of the hypnotist, what may we not await from any truly scientific knowledge of mind, comparable even in low degree to our knowledge of, say, electricity? But these in a sense are all details, relevant in a way, and yet only details. There is something still more fundamental in the biologist’s attitude. He has to study evolution, and in that study there is brought home to him, more vividly than to any one to whom the facts are not so familiar, that in spite of all appearances to the contrary there has been, throughout the whole of evolution, and most markedly in the rise of man from his pre-human forbears, a real advance, a progress.