Leaving now the description of these special [445] cases, we may resume our theoretical discussion of the subject, and try to get a clearer insight into the analogy of ever-sporting varieties and the wild species quoted. All of them may be characterized by the general term of dimorphism. Two types are always present, though not in the same individual or in the same organ. They exclude one another, and during their juvenile stage a decision is taken in one direction or in the other. Now, according to the theory of natural selection, wild species can only retain useful or at least innocuous qualities, since all mutations in a wrong direction must perish sooner or later. Cultivated species on the other hand are known to be largely endowed with qualities, which would be detrimental in the wild condition. Monstrosities are equally injurious and could not hold their own if left to themselves. These same principles may be applied to ever-sporting or antagonistic pairs of characters. According to the theory of mutations such pairs may be either useful or useless. But only the useful will stand further test, and if they find suitable conditions will become specific or varietal characters. On this conclusion it becomes at once clear, why natural dimorphism is, as a rule, a very useful quality, while the cultivated dimorphous varieties [446] strike us as something unnatural. The relation between cause and effect, is in truth other than it might seem to be at first view, but nevertheless it exists, and is of the highest importance. From this same conclusion we may further deduce some explanation of the hereditary races characterized by monstrosities. It is quite evident that the twisted teasels are inadequate for the struggle with their tall congeners, or with the surrounding plants. Hence the conclusion that a pure and exclusively twisted race would soon die out. The fact that such races are not in existence finds its explanation in this circumstance, and therefore it does not prove the impossibility or even the improbability that some time a pure twisted race might arise. If chance should put such an accidental race in the hands of an experimenter, it could be protected and preserved, and having no straight atavistic branches, but being twisted in all its organs, might yield the most curious conceivable monstrosity, surpassing even the celebrated dwarf twisted shrubs of Japanese horticulturists.