afterwards called germ-plasm, in that it always occupied a separate “sphere” of its own, where its continuity has been uninterrupted “since the first origin of life.” But Galton was not seduced by the temptation to construct an ideally logical system; and he had what I regard as the sound judgement to abstain from carrying his theory of stirp into any such transcendental “sphere” as that which is occupied by Weismann’s theory of germ-plasm, in relation to the general doctrine of descent. * * * * * There is, then, a vast distinction between any theory of heredity which postulates the material of heredity as highly stable and largely continuous, and Weismann’s theory, which postulates this material as absolutely stable and perpetually continuous. But we must next take notice that Weismann himself has not kept this distinction in view with the constancy which we should have expected from so forcible a thinker. On the contrary, although in the construction of his theory of evolution he never fails to press the postulates of _absolute_ stability and _perpetual_ continuity to their logical conclusions in the various doctrines above enumerated (pp. 57-58), when engaged on his more special theory of heredity he every now and then appears to lose sight of the distinction. Indeed, he occasionally makes such large concessions with regard to both these postulates, that, were they to be entertained, the occupation of his critics would be gone: his theory of heredity would become converted into Galton’s, while his theory of evolution would vanish altogether. It is therefore necessary to quote some of these concessions, if only to justify ourselves in subsequently ignoring them. I will give one instance of each; but it is necessary to preface the illustrations with a few words to mark emphatically three very distinct cases of congenital variation—leaving aside for the present the question whether or not they all occur in fact, as they are held to do by one or other of the theories of heredity. 1. The case where impoverished nutrition of the body has the effect of simply _starving_ its germinal material. This is not a case where either the continuity or the stability of such material is affected. Its full efficiency as “formative material” may indeed be thus deteriorated to any extent, so that the progeny may be to any extent puny or malformed; but this will not necessarily cause any such re-shuffling of its “molecules” as will thereafter result in a permanent phylogenetic change. At most it will affect only the immediate offspring of poorly nourished parents; and natural selection will always be ready to eliminate such inefficient individuals. This case I will always hereafter call the case of _nutritive_ congenital changes.