It does not appear to me that very much has to be said, either for or against the former postulate, on merely antecedent grounds, or grounds of general reasoning. Therefore I relegated to an Appendix my examination of what Weismann has argued on these grounds, while in the text I considered only what he has advanced as evidence _a posteriori_. Here, as we saw, he has developed three distinct lines of verification—viz. (A) the migration of germ-cells in some of the _Hydromedusae_,(B) the early separation of germ-cells in the ontogeny of certain Invertebrata, and (C) the alleged invariability of organisms which are produced parthenogenetically. But we have seen, with respect to (A), that the specialized character of germinal cells is a fact which every theory of heredity must more or less recognize; and, therefore, that the migration of these cells, wherever it may be found to occur, does not lend any peculiar countenance to Weismann’s theory. There may be many reasons for such migration other than the one which this theory assigns; while the reason which it does assign is rendered improbable by the consideration that in the _Hydromedusae_ the material of heredity is already and richly diffused throughout the general tissues. (B) and (C) are both contrary to fact; and, therefore, in whatever measure they would have corroborated the theory had they proved to be true, in that measure must they be held to discountenance the theory now that they have been shown to be false. It appears, then, that there is no evidence in support of the postulate of the _perpetual_ continuity of germ-plasm. There is nothing to show the necessary non-inheritance of acquired characters. The only evidence which one can recognize as good, is that which makes equally in favour of the theory of stirp—or rather, of the well-known fact that congenital characters are at any rate much _more_ heritable than are acquired: which, it is needless to repeat, is a widely different thing from proving—or even rendering probable—the _absolute_ restriction of germ-plasm to a separate “sphere” of its own “since the origin of life.”