EVOLUTION—ITS MEANING
other trustees which will carry that organization on and into the future." [1]
The reality of evolution in organic life once admitted, the next step must be to trace the details of its operation. For we recognize no "law of evolution" as working without regard to conditions. Evolution in vacuo is a philosophic fancy. Conclusions resting on analogies, or on the juggling of words, are not a part of science. "Living organisms," says Dr. Osborn, "differ from lifeless mechanisms, no matter how perfect, in being more or less self-adapting, self-reforming, self-perfecting, self-regenerating, self-modifying, self-resourceful, self-experimental, self -creative." In other words, they possess—
- Individuality: No two organisms are exactly alike.
- Irritability: The response to external stimulus, every organism being either swayed by influences bearing upon it or else reacting against them. Through evolution this response rises by degrees to tropism — the tendency to react in a definite manner — and to reflex action, with its specialized derivatives, instinct and intelligence.
- Reproduction: The casting off of specialized cells, each one of which (usually united with its mate through amphimixis) initiates a new individual.
- Metabolism: The wearing away of tissues and their replenishment by food derived from the substance of other organisms, or from water and from air.
- Growth: The development in size and in specialization of the fertilized cell, which is followed by deterioration and death, except in one-celled organisms, where we have cell division instead of death.
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