This is true of most of the Epidendra of South America, and of _Coryanthus triloba_ of New Zealand, two hundred blossoms of which only yielded five seed-capsules, and also of our _Ophrys muscifera_ and _O. aranifera_, the latter of which yielded only a single seed-capsule from 3,000 flowers gathered in Liguria. We might expect that the species in question must have become very rare, but this is not always the case, since each of these capsules contains an enormous number of seeds, sometimes many thousands. As soon as the visits of insects cease altogether, the species must die out in the particular locality concerned, unless it can revert to self-pollination and self-fertility. There is a whole series of species in which the stigma of the flower is sensitive to its own pollen, and in many of these an adaptation to self-fertilization has actually been effected, for the pollinia detach themselves from their anthers at maturity and fall upon the stigma. I have already mentioned _Ophrys apifera_, which, according to Charles Darwin, is no longer visited by insects, although its flowers still possess the structure required for insect-fertilization. This species has saved itself from extinction by the normal occurrence of self-fertilization. This seems to me noteworthy in two respects. In the first place, it shows that pure self-fertilization need not necessarily result in a weakening of the species, and secondly, it affords a clear instance of a species being transformed in one minute character only, all the other characters remaining unaltered. In this case it was only the pollinia that required to vary a little in their mode of attachment and maturation, in order to effect the transformation of the flower for self-fertilization, and in point of fact that is all that has varied. The case is not relevant to our investigation at this moment, but cases of the kind can so rarely be clearly demonstrated that I cannot lose the opportunity of calling attention to it. The germ-plasm of this _Ophrys_ must have varied at an earlier stage, for otherwise the detachment of the pollinia would not have become normal and hereditary, but it can only have varied to the extent that the structure of this one small part of the flower was affected by the variation; something must have varied in the germ-plasm that had no influence upon the other parts of the flower, that is, solely the _determinants_ of the pollinia.