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I shall therefore, from now on, use the term biological progress to denote movement in the direction which we have sketched in outline, and shall shortly proceed to define more accurately. In so doing, I perhaps beg the question, to be proved I hope later, as to whether the observed direction is progressive: but I no longer beg the question of whether evolution is a directional process. However we may argue on the facts, the facts remain: and the facts are that there has been an increase in certain qualities of organisms, both physical and mental, during geological time.

Meanwhile, let it be remembered, the simplest forms have survived side by side with the more complex, the less specialized with the more specialized. Even when we can trace a causal relation between the rise of one group and the decay of another, as with the mammals and birds on the one hand, and the reptiles on the other, even then numbers of the defeated group continue to exist. Thus, in broad terms, evolution is not a transformation, be it progressive or no, of the whole of living matter, but of a part of it.