Natural selection not inconsistent with natural theology : a free examination of Darwin's treatise On the origin of species, and of its American reviewers / by Asa Gray.

  • Asa Gray
Date:
1861
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Licence: Public Domain Mark

Credit: Natural selection not inconsistent with natural theology : a free examination of Darwin's treatise On the origin of species, and of its American reviewers / by Asa Gray. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    organic world, though they could not reconcile them; namely, Adap- tation to Purpose and to the Conditions of Existence, and Unity of Type. To reconcile these two undeniable principles is the capital prob- lem in the philosophy of natural history; and the hypothesis which con- sistently does so thereby secures a great advantage. We all know that the arm and hand of a monkey, the foreleg and foot of a dog and of a horse, the wing of a bat, and the fin of a porpoise are fundamentally identical; that the long neck of the giraffe has the same and no more bones than the short one of the elephant; that the eggs of Surinam frogs hatch into tadpoles with as good tails for swim- ming as any of their kindred, although as tadpoles they never enter the water; that the Guinea-pig is furnished jvith incisor teeth which it never uses, as it sheds them before birth ; that embryos of mammals and birds have branchial slits and arteries running in loops, in imita- tion or reminiscence of the arrangement which is permanent in fishes ; and that thousands of animals and plants have rudimentary organs which, at least in numerous cases, are wholly useless to their posses- sors, etc., etc. Upon a derivative theory this morphological conform- ity is explained by community of descent; and it has not been ex- plained in any other way. Naturalists are constantly speaking of “ related species,” of the “affinity” of a genus or other group, and of “family resemblance,” — vaguely conscious that these terms of kinship are something more than mere metaphors, but unaware of the grounds of their aptness. Mr. Darwin assures them that they have been talking derivative doctrine all their lives — as M. Jourdain talked prose — without knowing it. If it is difficult and in many cases practically impossible to fix the limits of species, it is still more so to fix those of genera; and those of tribes and families are still less susceptible of exact natural circumscrip- tion. Intermediate forms occur, connecting one group with another in a manner sadly perplexing to systematists, except to those who have ceased to expect absolute limitations in Nature. All this blending could hardly fail to suggest a former material connection among allied forms, such as that which an hypothesis of derivation demands. Here it would not be amiss to consider the general principle of gradation throughout organic Nature, — a principle which answers in a general way to the Law of Continuity in the inorganic world, or rather is so analogous to it that both may fairly be expressed by the Leibnitzian axiom, Natura non agit saltatim. As an axiom or philo- sophical principle, used to test modal laws or hypotheses, this in strict- ness belongs only to physics. In the investigation of Nature at large, at least *in the organic world, nobody would undertake to apply this principle as a test of the validity of any theory or supposed law. But
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