earth [page 79], and that of Dr. Wallace upon the exquisite adaptation between life and the earth to-day [page 91]. [Sidenote: The Study of Ferments] But how were those complex organic bodies formed, especially those vastly complex proteids with which all life whatsoever, as we know it, is invariably associated? Apart from the laboratories of the synthetic chemists of to-day, these compounds are always the products of pre-existing life, and yet without them there could be no pre-existing life. [Sidenote: Mystery of the Cell] [Sidenote: Is the Cell a Product of Evolution?] It is my belief that this most difficult question, which quite baffles us, will seem simple and straightforward in another generation, when science has devoted itself on a large scale to a study now in its very infancy--I mean the study of those curious bodies which chemists call ferments. The properties of ferments are shared both by the familiar ferments, such as trypsin and pepsin, and also by certain inorganic substances, such as the metal platinum. Now, though pepsin is a product of living cells, platinum is certainly not. Altogether apart from the living world there are substances which have powers of fermentation; and ferments do not act exclusively, as is erroneously supposed, in breaking down complex compounds, but also build them up from their constituents. The powers of a ferment, moreover, are, so far as we know, inexhaustible. All life whatever is exercised by ferments, and it is true that life, chemically considered, is “a series of fermentations.” Now, there is quite recent evidence already which seems to show that certain ferments, acting in suitable material, have the power of reproducing themselves--that is to say, of converting that material into their like. These facts are highly suggestive, and it is difficult to refrain from suggesting that the gap between living and lifeless matter, which seemed so absolute to our ancestors, and which even to us, who have a new conception of matter, seems wide enough, may yet be bridged by the ferments. We are far too apt, I think, to assume that when we can see no intermediate stage there were no intermediate stages, and thus to make difficulties for ourselves. We declare that life began as a single cell, which was the starting-point of organic evolution. I myself believe rather that the cell constitutes the acme of a vast epoch of evolution, which may yet be reproduced in brief in the laboratory. Denying or declining to think of this, the biologist who knows the amazing complexity and intricacy of the architecture of the cell may well decline to believe that such a thing could spring with a single jump from inorganic matter. We preach and go on preaching that Nature does nothing by jumps, and in the same breath we declare that life began as a simple cell. In another hundred years we may begin to realise that a cell in its own measure and on its own scale is an