neither appears except in the presence of the other. The inheritance of acquired characters is also made a corollary of monistic belief.
Now, all these hypotheses are possibly true, but none of them are as yet conclusions of science. They meet the conditions required by philosophy. They are plausible. They have the merit of logical continuity, and, excepting to those persons biased by early subjection to contrary notions, they satisfy the "human heart." There should be no natural repugnance to monism or to pantheism, difficult as it is to associate the idea of truth and reality with either or with the opposite of either. Speaking for myself, I feel no repugnance to them. They lend themselves to poetry; they appeal to the human heart. In Haeckel's own words, referring to something else, "such hereditary articles of faith take root all the more firmly, the further they are removed from the rational knowledge of Nature and enveloped in the mysterious mantle of mythological poesy." The present resistance to them may in time be turned into superstitious reverence for them; for, of all the philosophic doctrines brought down as lightning from heaven for the guidance of plodding man, these seem most attractive, and least likely to conflict with the conclusions of science.
But can we give them belief? Let us pass by the doctrine of monism, with which science can not concern itself. What of the corollaries? Spontaneous generation, for example, has been the basis of many experiments. Like the transmutation of metals, it seems reasonable to philosophy. The one idea has been the Will-o'-the-wisp of biology as the other has of chemistry. We know absolutely nothing of how, if ever, non-life becomes life. So far as we know, generation from first to last has been one unbroken series—"all life from life." We have no reason to believe that spontaneous generation exists under any conditions we have ever known. We have likewise reason to believe that if it exists at all we have no way of recognizing it. The organisms we know have all had a long history. Even the smallest shows traces of a long ancestry, a long process of natural selection, and of many concessions to environments. We know of no life that does not show such concessions. We know no creature that does not show homologies with all other living beings whatsoever. So far as this fact goes, it tends to show that all life is one. If this is true, spontaneous generation, whatever it may be, is not one of the ever-present phenomena of life.
If life does now appear without living parentage, if organisms fresh from the mint of creation now appear from inorganic matter, they are so simple that we can not know them. They are so small that we can not find them. They would be made, we may suppose, each of a small number of molecules. If there is truth in
