Let us return after this digression to our previous train of thought; we have to inquire how we can interpret the fact of continued self-fertilization without any visible injurious results to the species. If cross-fertilization be a material advantage as regards the continuance of the species, how can it be transformed into its opposite without evil effects? And there are no visible evil effects in _Ophrys apifera_. It is indeed not so abundant as _Ophrys muscifera_, or other allied species, but it certainly does not follow from that that it is on the way to extinction; certainly no decrease either of vigour of growth or of fertility can be observed. If we inquire from the standpoint of our theory, how the composition of the germ-plasm must have altered through continual inbreeding, we have already found the answer--that through the reduction of the number of ids at the maturation of every germ-cell the diversity of the germ-plasm would gradually be lessened, that the number of different ids would thereby be lessened possibly even to the identity of the whole of the ids. The consequences of such extreme uniformity of the germ-plasm would not, according to our theory, necessarily be that the species would be incapable of continued existence, but it would be that the species would become incapable of adaptations in many directions. Adaptations in one direction, such, for instance, as the variation in the mode of attachment and detachment of the pollinia of an Orchid, would still be possible. Thus a species which has long been perfectly adapted will be able to make the transition to inbreeding without injury to its chances of continued existence, if it be compelled by circumstances to do so. Species, on the other hand, which are still undergoing considerable transformations in many directions must be exposed by these to the danger of degeneration, just as happens in the artificial experiments with domesticated animals, whose secret weaknesses are greatly exaggerated by inbreeding. We might be inclined to regard the effects of inbreeding as similar to those of parthenogenesis; they are certainly analogous, for both modes of reproduction must lead to a certain degree of uniformity in the germ-plasm. But there seems to me to be a difference and one which is not without importance.