to a minuteness without conceivable limit, in effect, a minuteness that is beyond all finite measure or conception.  So that, as modern physics and optics have enabled us not to conceive merely, but to actually realize, the vastness of spatial extension, side by side with subtile tenuity and extreme divisibility of matter, so the labor, enthusiasm, and perseverance of thirty years, stimulated by the insight of a rare and master mind, and aided by lenses of steadily advancing perfection, have enabled the student of life-forms not simply to become possessed of an inconceivably broader, deeper, and truer knowledge of the great world of visible life, of which he himself is a factor, but also to open up and penetrate into a world of minute living things so ultimately little that we cannot adequately conceive them, which are, nevertheless, perfect in their adaptations and wonderful in their histories.  These organisms, while they are the least, are also the lowliest in nature, and are to our present capacity totally devoid of what is known as organic structure, even when scrutinized with our most powerful and perfect lenses.  Now these organisms lie on the very verge and margin of the vast area of what we know as living.  They possess the essential properties of life, but in their most initial state.  And their numberless billions, springing every moment into existence wherever putrescence appeared, led to the question, How do they originate?  Do they spring up de novo from the highest point on the area of not-life, which they touch?  Are they, in short, the direct product of some yet uncorrelated force in nature, changing the dead, the unorganized, the not-living, into definite forms of life?  Now this is a profound question, and that it is a difficult one there can be no doubt.  But that it is a question for our laboratories is certain.  And after careful and prolonged experiment and research the legitimate question to be asked is, Do we find that, in our laboratories and in the observed processes of nature now, the not-living can be, without the intervention of living things, changed into that which lives?

To that question the vast majority of practical biologists answer without hesitancy, No, we have no facts to justify such a conclusion.  Prof.  Huxley shall represent them.  He says:  “The properties of living matter distinguish it absolutely from all other kinds of things;” and, he continues, “the present state of our knowledge furnishes us with no link between the living and the not-living.”  Now let us carefully remember that the great doctrine of Charles Darwin has furnished biology with a magnificent generalization; one indeed which stands upon so broad a basis that great masses of detail and many needful interlocking facts are, of necessity, relegated to the quiet workers of the present and the earnest laborers of the years to come.  But it is a doctrine which cannot be shaken.  The constant and universal action of variation, the struggle for existence, and