Let us first of all seek to gain clearness as to the composition of the germ-plasm in the case of purely asexual multiplication, and what conclusions may be drawn from this, and then let us compare these with the known observational data, and it will be apparent that in individuals which have arisen by budding the complete germ-plasm of the species must be contained; the number of ids will not only remain the same in the bud as it was in the mother plant, but the number of _different ids_ will not be diminished. The case is analogous to that of pure parthenogenesis, in which the absence of the second maturation-division of the ovum allows the germ-plasm to retain the full complement of ids. Charles Darwin held that purely asexual multiplication was 'closely analogous to long-continued self-fertilization,' yet, as we have seen, according to our theory there must be a not inconsiderable difference between the two processes, depending on the fact that in exclusive self-fertilization the number of different ids is continually decreasing, while in purely asexual reproduction the germ-plasm loses nothing of the diversity of its ids. If, therefore, the germ-plasm in purely asexual reproduction no longer receives fresh ids through amphimixis, it at least loses none of those it formerly possessed. Although we cannot consider it adapted for entering upon new adaptations in many directions, yet we may expect that the species will continue to reproduce unchanged for longer than in the case of exclusive self-fertilization, the more so since all unfavourable variational tendencies which crop up are eliminated as soon as they attain to selection-value, and, as in the case of parthenogenesis, they are eliminated without being mingled with other lines of descent. Let us take, for instance, the purely asexual reproduction which obtains in Algæ of the genus _Laminaria_, in regard to which it is stated that it multiplies only through asexual swarm-spores. There are quite a number of species of this large tangle, and if it should be established that in all these the spore-cells really do not conjugate, then the case would prove that the species of a genus can maintain a well-defined existence for a long time after amphimixis has been given up. But this would not be a proof of the possibility of _species-formation_, for that the ancestral forms of the Laminarians must have possessed amphigony may be assumed, since their nearest relatives exhibit it still. It cannot be proved, but there seems nothing against the assumption that these tangles have existed for a long time under uniform conditions, and have become adapted to these with a high degree of constancy. The conditions are similar in the marine Algæ of the genus _Caulerpa_, the nearest relatives of which reproduce sexually, though they themselves, as far as is known, reproduce only by spores.