From this it would seem, that spontaneous crosses are hurtful to varieties, but are innocuous to true species. Certainly this would be so, were there no selection. But it is easily seen, that through this operation the effect becomes quite the opposite. For when the fields [210] are inspected at the time of the fullest display of the varietal characters, the obvious hybrids will be eliminated, but the hidden ones will of necessity be spared, as they are concealed among the species by the similarity of their type. Hence, the harvest of the variety may be rendered pure or nearly so, while the harvest of the species will retain the seeds of the hybrids. Moreover it will contain seeds originated by the spontaneous but numerous crosses of the true plants with the sparsely intermingled hybrids. This brings us to the question, as to what will be the visible consequences of the occurrence of such invisible hybrids in the following generation. In opposition to the direct effects just described, we may call them indirect. To judge of their influence, we must know how hybrid seeds of the first generation behave. In one of our lectures we will deal with the laws that show the numerical relations known as the laws of Mendel. But for our present purpose, these numerical relations are only of subordinate importance. What interests us here is the fact that hybrids of varieties do not remain constant in the second generation but usually split as it is said, remaining hybrid only in part of their offspring, the other portion returning to the parental types. This however, will show itself only in those individuals [211] which reassume the character of the varietal parent, all the others apparently remaining true to the type of the species. Now it is easy to foresee what must happen in the second generation if the first generation after the cross is supposed to be kept free from new vicinistic influences, or from crosses with neighboring varieties. We may limit ourselves in the first place to the seeds of the unobserved hybrids. For the greater part they will repeat the character of their parents and still remain concealed. But a small number will display the varietal marks, as for example showing white flowers in a field of blue ones. Hence, the indirect consequence of the spontaneous crosses will be the same in the species, as was the direct effect in the variety, only that it appears a year later. It will then be eliminated in the process of selection. Obviously, this elimination conduces only to a partial purification. The conspicuous plants will be destroyed, but a greater number of hybrids will remain, still concealed by their resemblance to the general type and will be spared to repeat the same process next year. So while the variety may be freed every year from the impurities brought into it in the preceeding summer, the admixtures of the species [212] will continue during a number of years, and it may not be possible to get rid of them at all.