Philosophical Transactions of the Royal Society for the Year 1821, Part I, pp. 20-24.
It will, I suppose, be said that the non-inheritance of mutilations constitutes evidence of the kind here asked for. The first reply is that the evidence is conflicting, as it may well be. It is forgotten that to have valid evidence of non-inheritance of mutilations, it is requisite that both parents shall have undergone mutilation, and that this does not often happen. If they have not, then, assuming the inheritableness of mutilations, there would, leaving out other causes, be an equal tendency to appearance and non-appearance of the mutilation in offspring. But there is another cause—the tendency to reversion, which ever works in the direction of cancelling individual characters by the return to ancestral characters. So that even were the inheritance of mutilations to be expected (and for myself I may say that its occurrence surprises me), it could not be reasonably looked for as more than exceptional: there are two strong countervailing tendencies. But now, in the second place, let it be remarked that the inheritance or non-inheritance of mutilations is beside the question. The question is whether modifications of parts produced by modifications of functions are inheritable or not. And then, by way of disproof of their inheritableness, we are referred to cases in which the modifications of parts are not produced by modifications of functions, but are otherwise produced!
See First Principles, Part II, Chap. XXII, "Equilibration."
Principles of Biology, § 46, (No. 8. April, 1863).
Ibid. This must not be understood as implying that while the mass increases as the cubes, the quantity of motion which can be generated increases only as the squares; for this would not be true. The quantity of motion is obviously measured, not by the sectional areas of the muscles alone, but by these multiplied into their lengths, and therefore increases as the cubes. But this admission leaves untouched the conclusion that the ability to bear stress increases only as the squares; and thus limits the ability to generate motion, by relative incoherence of materials.