The absence of _diurna_ in such localities may fairly be construed as an indication that _diurna_ is there at a real disadvantage in the competition for life. But if, admitting this, we proceed to consider how the special aptitude of _vespertina_ is constituted, or what it is that puts _diurna_ at a disadvantage, we find ourselves quite unable to show the slightest connexion between the success of one or the failure of the other on the one hand, and _the specific characteristics_ which distinguish the two forms on the other. The orthodox Selectionist would, as usual, appeal to ignorance. We ask what can _vespertina_ gain by its white flowers, its more lanceolate leaves, its grey seeds, its almost erect capsule-teeth, its longer fruits, which _diurna_ loses by reason of its red flowers, more ovate leaves, dark seeds, capsule-teeth rolled back, and shorter fruits? We are told that each of these things _may_ affect the viability of their possessors. We cannot assert that this is untrue, but we should like to have evidence that it is true. The same problem confronts us in thousands upon thousands of examples, and as time goes on we begin to feel that speculative appeals to ignorance, though dialectically admissible, provide an insufficient basis for a proposition which, if granted, is to become the foundation of a vast scheme of positive construction. One thing must be abundantly clear to all, that to treat two forms so profoundly different as one, because intermediates of unknown nature can be shown to exist between them, is a mere shirking of the difficulties, and this course indeed creates artificial obstacles in the way of those who are seeking to discover the origin of organic diversity. In the enthusiasm with which evolutionary ideas were received the specificity of living things was almost forgotten. The exactitude with which the members of a species so often conform in the diagnostic, specific features passed out of account; and the scientific world by dwelling with a constant emphasis on the fact of variability, persuaded itself readily that species had after all been a mere figment of the human mind. Without presuming to declare what future research only can reveal, I anticipate that, when variation has been properly examined and the several kinds of variability have been successfully distinguished according to their respective natures, the result will render the natural definiteness of species increasingly apparent. Formerly in such a case as that of the two _Lychnis_ species, the series of "intermediates" was taken to be a palpable proof that _vespertina_ "graded" to _diurna_. It is this fact, doubtless, upon which Bentham would have relied in suggesting that both may be one species.[13] Genetic tests, though as yet imperfectly applied, make it almost certain that these inter-grading forms are not in any true sense variations from either species in the direction of the other, but combinations of elements derived from both.