while, therefore, to consider whether the phrase, "derivation from the lower animals," is one which can be maintained as rightly expressing the truth which it is intended to express concerning the physical history of our race.
Now it is manifest that if we look back, so far as is possible, into the remote past, when the first germ of animal life appeared upon the globe, two conditions of things, and two only, are conceivable. Either (A) there was a single germ of life, from which all subsequent living forms have been evolved or developed; or (B) there were several or many germs of life, from which, in separate streams, so to speak, the evolution of living creatures took place. Mr. Darwin inclined, I think, to the latter supposition; but either A or B must be accepted by all evolutionists of all schools. Let us consider them successively.
A. If we make the supposition that living forms commenced upon the globe from a single germ, then it follows that all living creatures now existing—insects, fishes, birds, beasts, man—have been evolved by some process or processes from one and the same origin: whether the process of variation and natural selection be sufficient to account for the development, it is not necessary for the purpose of this argument to decide; it is sufficient to say, and this can scarcely be denied, that by some process or processes the development has taken place. Therefore, ascending to the hypothesis now under consideration, it will be true that the lower animals and man had a common origin; but this is manifestly a different thing from asserting that man is "derived from the lower animals." If we go up to the hypothetical origin of life, or the single germ, this latter assertion is obviously untrue, because, as by hypothesis there was then only one germ, there could be no distinction of superior or inferior; but if we stop short of the origin and observe the condition of things at any period subsequent to the hypothetical beginning, we shall find progress being made toward the development of man and simultaneous progress being made toward the development of the lower animals. But it does not follow that, because this simultaneous development is taking place, therefore we can say that one form of life is developed from the other; it might be as correct to say that the inferior animals were developed from man, as man from the inferior animals. Take an illustration from that which is possible in the case of rivers. Conceive of two rivers running into the sea; trace their course, and suppose that ultimately you come to the same source in the distant mountains; it would not be correct to say that one of these rivers was derived from the other. The correct statement would be that they sprang from one and the same source, that they had different histories, and that they terminated in different streams.