Omission of the consideration of difference, it is to be acknowledged, is not now-a-days restricted to Mr. Huxley. In the wonder that is usually expressed, for example, at Oken’s _identification_ of the skull with so many vertebræ, it is forgot that there is still implicated the wonder which we ought to feel at the unknown power that could, in the end, so _differentiate_ them. If the cornea of the eye and the enamel of the teeth are alike but modified protoplasm, we must be pardoned for thinking more of the adjective than of the substantive. Our wonder is how, for one idea, protoplasm could become one thing here, and, for another idea, another so different thing there. We are more curious about the modification than the protoplasm. In the difference, rather than in the identity, it is, indeed, that the wonder lies. Here are several thousand pieces of protoplasm; analysis can detect no difference in them. They are to us, let us say, as they are to Mr. Huxley, identical in power, in form, and in substance; and yet on all these several thousand little bits of apparently indistinguishable matter an element of difference so pervading and so persistent has been impressed, that, of them all, not one is interchangeable with another! Each seed feeds its own kind. The protoplasm of the gnat will no more grow into the fly than it will grow into an elephant. Protoplasm is protoplasm: yes, but man’s protoplasm is man’s protoplasm, and the mushroom’s the mushroom’s. In short, it is quite evident that the word modification, if it would conceal, is powerless to withdraw, the difference; which difference, moreover, is one of kind and not of degree. This consideration of possible objections, then, is the last we have to attend to; and it only remains to draw the general conclusion. All animal and vegetable organisms are alike in power, in form, and in substance, only if the protoplasm of which they are composed is similarly alike; and the functions of all animal and vegetable organisms are but properties of the molecular affections of their chemical constituents, only if the functions of the protoplasm, of which they are composed, are but properties of the molecular affections of _its_ chemical constituents. In disproof of the affirmative in both clauses, there has been no object but to demonstrate, on the one hand, the infinite non-identity of protoplasm, and, on the other, the dependence of its functions upon other factors than its molecular constituents. In short, the whole position of Mr. Huxley, that all organisms consist alike of the same life-matter, which life-matter is, for its part, due only to chemistry, must be pronounced untenable—nor less untenable the materialism he would found on it. ------------------------------------------------------------------------ _ON THE HYPOTHESIS OF EVOLUTION_: PHYSICAL AND METAPHYSICAL. ------------------------------------------------------------------------