As was said at the beginning of this chapter, "Pangenesis" and "Natural Selection" are quite separable and distinct hypotheses. The fall of one of these by no means necessarily includes that of the other. Nevertheless, Mr. Darwin has associated them closely together, and, therefore, the refutation of Pangenesis may render it advisable for those who have hitherto accepted "Natural Selection" to reconsider that theory.
CHAPTER XI.
SPECIFIC GENESIS.
Review of the statements and arguments of preceding chapters.—Cumulative argument against predominant action of "Natural Selection."—Whether anything positive as well as negative can be enunciated.—Constancy of laws of nature does not necessarily imply constancy of specific evolution.—Possible exceptional stability of existing epoch.—Probability that an internal cause of change exists.—Innate powers must be conceived as existing somewhere or other.—Symbolism of molecular action under vibrating impulses.—Professor Owen's statement.—Statement of the Author's view.—It avoids the difficulties which oppose "Natural Selection."—It harmonizes apparently conflicting conceptions.—Summary and conclusion.
Having now severally reviewed the principal biological facts which bear upon specific manifestation, it remains to sum up the results, and to endeavour to ascertain what, if anything, can be said positively, as well as negatively, on this deeply interesting question.
In the preceding chapters it has been contended, in the first place, that no mere survival of the fittest accidental and minute variations can account for the incipient stages of useful structures, such as, e.g., the heads of flat-fishes, the baleen of whales, vertebrate limbs, the laryngeal structures of the newborn kangaroo, the pedicellariæ of Echinoderms, or for many of the facts of mimicry, and especially those last touches of mimetic perfection, where an insect not only mimics a leaf, but one worm-eaten and attacked by fungi.
Also, that structures like the hood of the cobra and the rattle of the rattlesnake seem to require another explanation.