The basal idea of the essay--the existence of Germinal Selection--was propounded by me some time since,[1] but it is here for the first time fully set forth and tentatively shown to be the necessary complement of the process of selection. Knowing this factor, we remove, it seems to me, the patent contradiction of the assumption that the general fitness of organisms, or the adaptations _necessary_ to their existence, are produced by _accidental_ variations--a contradiction which formed a serious stumbling-block to the theory of selection. Though still assuming that the _primary_ variations are "accidental," I yet hope to have demonstrated that an interior mechanism exists which compels them to go on increasing in a definite direction, the moment selection intervenes. _Definitely directed {4} variation exists_, but not predestined variation, running on independently of the life-conditions of the organism, as Naegeli, to mention the most extreme advocate of this doctrine, has assumed; on the contrary, the variation is such as is elicited and controlled by those conditions themselves, though indirectly. In basing my proof of the doctrine of Germinal Selection on the fundamental conceptions of my theory of heredity, a few words of justification are necessary, owing to the fact that the last-mentioned theory has been widely and severely assailed since its first emergence into light and even repudiated as absolutely futile and erroneous. In the first place, many critics have characterised it as a "pure creation of the imagination." And to a certain extent it is such, as every theory is. But is it on that account necessarily wrong? Can not its fundamental ideas still be quite correct, and it itself therefore perfectly justified as a means of further progress?