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 the "survival of the fittest," few who are competent to grasp will have the temerity to doubt. And to many, that lies within it as a doctrine, and forms the fibre of its fabric, is the existence of a continuity, an unbroken stream of unity running from the base to the apex of the entire organic series. The plant and the animal, the lowliest organized and the most complex, the minutest and the largest, are related to each other so as to constitute one majestic organic whole. Now to this splendid continuity practical biology presents no adverse fact. All our most recent and most accurate knowledge confirms it. But _the_ question is, Does this continuity terminate now in the living series, and is there then a break--a sharp, clear discontinuity, and beyond, another realm immeasurably less endowed, known as the realm of not-life? or Does what has been taken for the clear-cut boundary of the vital area, when more deeply searched, reveal the presence of a force at present unknown, which changes not-living into the living, and thus makes all nature an unbroken