The factorial mutant answers neither the endurance test nor the intersterility test of a genuine species. It would, doubtless, be going too far to regard all such mutant forms as examples of germinal degeneracy, but it cannot be denied that all of them, when compared to the wild type, are in the direction of unfitness, none of them being viable and prosperous under the severe conditions obtaining in the wild state. Bateson, who seems to regard all mutant characters as recessive and due to germinal loss, declares: “Even in Drosophila, where hundreds of genetically distinct factors have been identified, very few new dominants, that is to say positive additions, have been seen, and I am assured that none of them are of a class which could be expected to be viable under natural conditions. I understand even that none are certainly viable in the homozygous state.” (Toronto Address, _Science_, Jan. 20, 1922, p. 59.) “Garden or greenhouse products,” says D. S. Jordan, “are immensely interesting and instructive, but they throw little light on the origin of species. To call them species is like calling dress-parade cadets ‘soldiers.’ I have heard this definition of a soldier, ‘one that has stood.’ It is easy to trick out a group of boys to look like soldiers, but you can not define them as such until they have ‘stood.’” (_Science_, Oct. 20, 1922.) In a word, factorial mutants, owing, as they do, their survival exclusively to the protection of artificial conditions, could never become the hardy pioneers of new species.