The last few lectures will be devoted to questions concerning the great problem of the analogy between natural and artificial selection. As already stated, Darwin made this analogy the foundation stone of his theory of descent, and he met with the severest objections and criticisms precisely on this point. But I hope to [19] show that he was quite right, and that the cause of the divergence of opinions is due simply to the very incomplete state of knowledge concerning both processes. If both are critically analyzed they may be seen to comprise the same factors, and further discussion may be limited to the appreciation of the part which each of them has played in nature and among cultivated plants. Both natural and artificial selection are partly specific, and partly intra-specific or individual. Nature of course, and intelligent men first chose the best elementary species from among the swarms. In cultivation this is the process of variety-testing. In nature it is the survival of the fittest species, or, as Morgan designates it, the survival of species in the struggle for existence. The species are not changed by this struggle, they are only weighed against each other, the weak being thrown aside. Within the chosen elementary species there is also a struggle. It is obvious, that the fluctuating variability adapts some to the given circumstances, while it lessens the chances of others. A choice results, and this choice is what is often exclusively called selection, either natural or artificial. In cultivation it produces the improved and the local races; in nature little is known about improvement in this way, but [19] local adaptations with slight changes of the average character in separate localities, seem to be of quite normal occurrence. A new method of individual selection has been used in recent years in America, especially by W.M. Hays. It consists in judging the hereditary worth of a plant by the average condition of its offspring, instead of by its own visible characters. If this determination of the "centgener power," as Hays calls it, should prove to be the true principle of selection, then indeed the analogy between natural and artificial selection would lose a large part of its importance. We will reserve this question for the last lecture, as it pertains more to the future, than to our present stock of knowledge.