II.

EVOLUTION: WHAT IT IS AND WHAT IT IS NOT.

What evolution is.

THIS is the age of evolution. The word is used by many men in many senses, and still oftener perhaps in no sense at all. By some it is spoken with a haunting dread, as though it were another name for the downfall of religion and of social stability. Still others speak it glibly and joyously, as though progress and freedom were secured by the mere use of the name. "The word evolution (Entwickelung)," says a German writer, "fills the vocal cords more perfectly than any other word." It explains everything and "puts the key to the universe into one's vest pocket."

So various has been the use of the word, so rarely is this use associated with any definite idea, that one hesitates to call himself an evolutionist. Evolution" and "evolutionist are almost ready to be cast into that "limbo of spoiled phraseology" which Matthew Arnold has found necessary for so many words in which other generations delighted and which they soiled or spoiled by careless usage.

But as the word evolution is not yet put away, as it is the bugbear of many good people and the "religion of as many more equally good, it may be worth while to consider what it still means and what it does not mean, for if we that use the word can agree on a definition half our quarrel is over.

1

It seems to me that the word evolution is now legitimately used in four different senses. It is the name of

a branch of science; it is a theory of organic existence; it is a method of investigation; and it is the basis of a system of philosophy.

The science of organic evolution.

As a science, evolution is the study of changing beings acted upon by unchanging laws. It is a matter of common observation that organisms. change from day to day, and that day by day some alteration in their environment is produced. It is a conclusion from scientific investigation that these changes are greater than they appear. They affect not only the individual animal or plant, but they affect all groups of living things, classes or races or species. No character is permanent, no trait of life without change; and as the living organism and groups of organisms are undergoing alteration, so does change take place in the objects of the physical world about them. "Nothing endures," says Huxley, "save the flow of energy and the rational order that pervades it." The structures and objects change their forms and relations, and to forms and relations once abandoned they never return; but the methods of change are, so far as we can see, immutable. The laws of life, the laws of death, and the laws of matter never change. If the invisible forces which rule all visible things are themselves subject to modification and evolution we have not detected it. If these vary, their aberrations are so fine as to defy human observation and computation. In the control of the universe we find no trace of “variableness nor shadow of turning." "It is the law of heaven and earth, whose way is solid, substantial, vast, and unchanging."

But the things we know do not endure. Only the shortness of human life allows us to speak of species or

even of individuals as permanent entities. The mountain chain is no more nearly eternal than the drift of sand. It endures beyond the period of human observation; it antedates and outlasts human history. So does the species of animal or plant outlast and antedate the lifetime of one man. Its changes are slight even in the lifetime of the race. Thus the species, through the persistence of its type among its changing individuals, comes to be regarded as something which is beyond modification, unchanging so long as it exists.

"I believe," said the rose to the lily in the parable, "I believe that our gardener is immortal. I have watched him from day to day since I bloomed, and I see no change in him. The tulip who died yesterday told me the same thing."

As a flash of lightning in the duration of the night, so is the life of man in the duration of Nature. When one looks out on a storm at night he sees for an instant the landscape illumined by the lightning flash. All seems at rest. The branches in the wind, the flying clouds, the falling rain, are all motionless in this instantaneous view. The record on the retina takes no account of change, and to the eye the change does not exist. Brief as the lightning flash in the storm is the life of man compared with the great time record of life upon earth. To the untrained man who has not learned to read these records, species and types in life are enduring. From this illusion arose the theory of special creation and permanence of type, a theory which could not persist when the fact of change and the forces causing it came to be studied in detail.

But when man came to investigate the facts of individual variation and to think of their significance, the current of life no longer seemed at rest. Like the flow of a mighty river, ever sweeping steadily on, never re

turning, is the movement of all life. The changes in human history are only typical of the changes that take place in all living creatures. In fact, human history is only a part of one great life current, the movement of which is everywhere governed by the same laws, depends on the same forces, and brings about like results.

The facts and generalizations of change constitute the subject matter of evolution; and as the fact of life is a fundamental one and in some degree modifies all phenomena which it concerns, we have as the central axis of the science in question the study of organic evolution. In fact, while inorganic evolution or orderly change in environment also exists, we do not know to what degree the laws and forces of organic evolution can be reduced to the same terms of expression. The theory of the essential and necessary unity of life and non-life, of mind and matter, is still a matter of philosophical speculation only. We can neither prove the truth of Monism nor understand it; nor is the contrary hypothesis either comprehensible or credible. The fundamental unity of organic evolution and inorganic evolution is likewise yet to be proved, while the laws which govern living matter are certainly in part peculiar to life. For this reason the evolution of astronomy, of dynamic geology, of geography, as well as the purely hypothetical evolution of chemistry, must be separated from life evolution. Cosmic evolution and organic evolution show or seem to show some divergence from each other. To regard them as identical is to introduce confusion and not order into our conception of evolution. There are some elements which are not held in common, or which at least are not identical when measured in human terms. It is not evident that any force in the evolution of life is homologous with any which has brought about the evolution of stars and planets. This

unity of forces may be a philosophical necessity; it is not a fact.

Bionomics.

For the science which treats of organic evolution we are in great need of a distinctive term. This need was met by Prof. Patrick Geddes, who suggested the term bionomics. Bionomics (Bíos, life; vóμos, law or custom) is the science which treats of the changes in life forms and of the laws and forces on which these changes depend.

Even as thus restricted, organic evolution, or bionomics, is the greatest of the sciences, including in its subject matter not only all natural history, not only processes like cell division and nutrition, not only the laws of heredity, variation, natural selection, and mutual help, but all matters of human history, and the most complicated relations of civics, economics, and ethics. In this enormous science no fact can be without a meaning, and no fact or its underlying forces can be separated from the great forces whose interaction from moment to moment writes the great story of life.

And as the basis to the science of bionomics, as to all other science, must be taken the conception that nothing is due to chance or whim. Whatever occurs comes as the resultant of moving forces. Could we know and estimate these forces, we should have, so far as our estimate is accurate and our logic perfect, the gift of prophecy. Knowing the law, and knowing the facts, we should foretell the results. To be able in some degree to do this is the art of life. It is the ultimate end of science, which finds its final purpose in human conduct.

"A law," according to Darwin, "is the ascertained sequence of events." The necessary sequence of events it is, in fact, but man knows nothing of what is necessary, only of what has been ascertained to occur. Be