survival-value but rather because none of their diversities was so damaging as to lead to the extermination of its possessor. When we see these various Veronicas each rigidly reproducing its parental type, all comfortably surviving in competition with each other, are we not forced to the conclusion that tolerance has as much to do with the diversity of species as the stringency of Selection? Certainly these species owe their continued existence to the fact that they are each good enough to live, but how shall we refer the distinctions between them directly or indirectly to the determination of Natural Selection?

The control of Selection is loose while the conformity to specific distinction is often very strict and precise, and no less so even when several closely related species co-exist in the same area and in the same circumstances.

The theory of Selection fails at exactly the point where it was devised to help: Specific distinction.

Let us examine a somewhat different set of facts in the case of another pair of nearly allied species Lychnis diurna and vespertina. The two plants have much in common. Both are dioecious perennials, with somewhat similar flowers, the one crimson, the other white. Each however has its peculiarities which are discernible in almost any part of its structure, whether flower, leaf, fruit or seed, distinctions which would enable a person thoroughly familiar with the plants to determine at once from which species even a small piece had been taken. There is so much resemblance however as readily to support the surmise that the two were mere varieties of one species. Bentham, following Linnaeus, in fact actually makes this suggestion, with what propriety we will afterwards consider. Now this case is typical of many. The two forms have a wide distribution, occurring sometimes separately, sometimes in juxtaposition. L. diurna is a plant of hedgerows and sheltered situations. L. vespertina is common in fields and open spaces, where diurna is hardly ever found; but not rarely vespertina occurs in association with diurna in the places which that plant frequents. In this case I do not doubt that we have to do with organisms of somewhat different aptitudes. That L. vespertina has powers which diurna has not is shown very clearly by the fact that diurna is sometimes entirely absent from areas where vespertina can abound.[9] But in order to understand the true genetic relations of the two plants to each other it is necessary to observe their behaviour when they meet as they not unfrequently do. If the Lychnis population of such a locality be examined it will be found to consist of many undoubted and unmodified diurna, a number—sometimes few, sometimes many—of similarly unmodified vespertina, and an uncertain but usually rather small proportion of plants obviously hybrids between the two. How is it possible to reconcile these facts with the view that specific distinction has no natural basis apart from environmental exigency?

Darwinian orthodoxy suggests that by a gradual process of Natural Selection either one of these two types was evolved from the other, or both from a third type. I cannot imagine that anyone familiar with the facts would propose the first hypothesis in the case of Lychnis, nor can I conceive of any process, whether gradual or sudden, by which diurna could have come out of vespertina, or vespertina out of diurna. Both however may no doubt have been derived from some original third type. It is conceivable that Lychnis macrocarpa of Boissier, a native of Southern Spain and Morocco, may be this original form. This species is said to combine a white flower (like that of L. vespertina), with capsule-teeth rolled back (like those of diurna).[10] But whatever the common progenitor may have been, if we are to believe that these two species have been evolved from it by a gradual process of Natural Selection based on adaptation, enormous assumptions must be made regarding the special fitness of these two forms and the special unfitness of the common parent, and these assumptions must be specially invoked and repeated for each several feature of structure or habits distinguishing the three forms.

Why, if the common parent was strong enough to live to give rise to these two species, is it either altogether lost now, or at least absent from the whole of Northern Europe? Its two putative descendants, though so distinct from each other, are, as we have seen, able often to occupy the same ground. If they were gradually derived from a common progenitor—necessarily very like themselves—can we believe that this original form should always, in all the diversities of soil and situation which they inhabit, be unable to exist? Some one may fancy that the hybrids which are found in the situations occupied by both forms are this original parental species. But nothing can be more certain than that these plants are simply heterozygous combinations made by the union of gametes bearing the characters of diurna and vespertina.[11] For they may be reproduced exactly in F₁ or in later generations of that cross when it is artificially made; when bred from their families exhibit palpable phenomena of segregation more or less complex; and usually, if perhaps not always, they are partially sterile.[12] In a locality on the Norfolk coast that I know well, there is a strip of rough ground chiefly sand-bank, which runs along the shore. This ground is full of vespertina. Not a hundred yards inland is a lane containing diurna, and among the vespertina on the sand-bank are always some of the hybrid form, doubtless the result of fertilisation from the neighbouring diurna population. Seed saved from these hybrids gave vespertina and hybrids again, having obviously been fertilised by other vespertina or by other hybrids, and I have no doubt that such hybrid plants if fertilised by diurna would have shown some diurna offspring. 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,