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EVOLUTION AND ANIMAL LIFE

CHAPTER I

EVOLUTION DEFINED

Grau, theurer Freund, ist alle Theorie,
Und grün des Lebens gold'ner Baum.
—GoFTHE.

Men of science repudiate the opinion that natural laws are rulers and governors of nature, looking with suspicion on all “necessary” and universal laws.-BRooks.

This volume treats of the elements of the science of Organic Evolution. To this science belongs the consideration of the forces which govern the changes in organisms. It includes the influences which control development in the individual and in the species which is the succession of individuals, together with the laws or observed sequences of events which development exhibits. From another point of view, this is the science of life—adaptation. The term Bionomics (Bös, life, véuðs, order or custom), first suggested by Prof. Patrick Geddes, is essentially equivalent to the older term Organic Evolution, the science of the facts, processes, and laws involved in the mutation of organisms. For many reasons, this new name, Bionomics, with its technically exact meaning, should be preferred to the phrase Organic Evolution, as, unlike the latter, it involves no philosophic assumptions.

That organs and organisms do change from day to day, and place to place, and from generation to generation is an observed fact, which now admits of no doubt. The orderly arrangement of our knowledge of this process constitutes a branch of science. To use the word evolution in regard to this process is to use a philosophic term in connection with a group of scientific facts. For the word evolution means unrolling. It carries the thought that something which was previously hidden is now brought to light. This leads naturally to the philosophic suggestion that whatever is evolved must be previously involved. This may be true as a matter of words, but not necessarily so as a matter of fact, unless we reduce these words to the simple meaning that the actual now must have been the possible before; whatever actually takes place was a possibility before it happened. The word evolution, then, belongs to philosophy rather than to science. In the philosophy of nature the idea that present conditions are brought about through unrolling or unveiling has had a long existence. The word evolution has been frequently applied to the process of growth and maturity of the individual animal or plant, and again to the process of derivation of species from ancestral organisms, and again to the progressive changes in the forms of inorganic bodies, as planets or mountains. Each one of these meanings is essentially distinct from the others, and each is distinct from the theory of evolution which existed in the dawn of biological science. When men first began to notice the changes in the animal embryo, through which, from the formless egg, little by little, the individual was built up, becoming at each stage of the process larger, more specialized, and more like the parent from which it sprang, it was natural to regard this process as an unrolling. It was natural, too, to suppose that the egg was not really formless, but that the beginnings of each part of the final organism existed within it in fact, if we could see them. Hence evolution took the form of a theory of encasement. Men imagined that the egg of the chicken contained a minute chicken, and that within this chicken were the germs of the eggs the future hen would bear; and again, that encased within each of these eggs was an endless series of the eggs and chickens of all the future. In like fashion, men conceived that in the small human egg were the bodies and embryos of countless future generations. In some theories, this idea of encasement was applied not to the egg, but to the male germ, the homunculus or minute man in whom the generations of the future were enfolded and from which they unrolled. The perfection of the microscope as an instrument of precision did not verify these theories of encasement. The egg still appeared essentially formless, a mass of undifferentiated

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