CREATION BY EVOLUTION
legs is identical with that seen in the leg of an ape; it is an adaptation that makes it easy to press the soles of the feet against opposite sides of a branch in climbing.
The repetition of ancestral phases in life histories has been compared to memory. If we learn tennis when we are young and have no time to practice it until middle life we shall nevertheless find that when we resume the game a part of our skill comes back to us, that, in a word, we remember it. So when salamanders have grown up in a yellow box and have become yellowed in consequence, their young "remember" the parental experience and strive to turn yellow in spite of being enclosed in black boxes. The tadpole represents a memory of the time when the ancestors of the frog lived like fish. But all development does not reflect purely ancestral experience. Just as memories become blurred and sometimes confused with the lapse of time, so secondary modifying factors tend to render the ancestral record of development illegible. The organs of a larva are used, broadly speaking, in much the same way as the ancestors used them, but the corresponding organs of an embryo are not used, and so these tend to be imperfectly developed and to degenerate into mere sketches of the ancestral organs. Larval life, which represents ancestral habits, may become excessively dangerous, and the larva, in self defence, may be driven to adopt another mode of life, as when the young of the May-fly learn to live in water and develop secondary gills. But these secondary modifications are usually peculiar in each kind of animal, and the fundamental ancestral record can be deciphered only by comparing a large number of life histories, just as the historian extracts the truth from ancient documents by stressing the points in which they agree and discounting those in which they differ.
The most direct proof of evolution is certainly afforded
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