Spencer claims that, since 1886, when he first published this argument, nothing like an adequate response has been made; and I think he might have added that an adequate answer is not likely to be forthcoming, since nothing short of a demonstration of how the giraffe really evolved is likely to be considered as sufficient. Wallace’s reply, that the changes in question could have been brought about by natural selection, since similar changes have been brought about by artificial selection, is regarded as inadequate by Spencer, since it assumes a parallel which does not exist. Nevertheless, Wallace’s reply contains, in my opinion, the kernel of the explanation, in so far as it assumes that congenital variation[19] may suffice to account for the origin of a form even as bizarre as that of the giraffe. The ancon ram and the turnspit dog were marked departures from the normal types, and yet their parts were sufficiently coördinated for them to carry out the usual modes of progression. It would not have been difficult, if we adopted Spencer’s mode of arguing, to show that these new forms could not possibly have arisen as the result of congenital variations. Footnote 19: Wallace assumes fluctuating variation to suffice, but in this I cannot agree with him. Again, it might be argued that the large, powerful dray-horse could not have arisen through a series of variations from the ordinary horse, because, even if variations in the right direction occurred in the fore-quarters, it is unlikely that similar variations would occur in the hind-quarters, etc. Yet the feat has been accomplished, and while it is difficult to prove that the inheritance of acquired characters has not had a hand in the process, it is improbable that this has been the case, but rather that artificial selection of some kind of variations has been the factor at work. So long as the Lamarckian theory is supported by arguments like these, it can never hope to be established with anything more than a certain degree of probability. If it is correct, then its demonstration must come from experiment. This brings us to a consideration of the experimental evidence which has been supposed by some writers to give conclusive proof of the validity of the theory.