would be chaotic and without significance. Thus, ever since Darwin's own attempt at a theory of heredity, we find the students of organic evolution and the breeders of plant and animal races alike devoting themselves to the problems of racial and individual inheritance.
Now it is plainly futile for the psychologist to pretend to firsthand knowledge in a field which is not his own; but, on the other hand, it is equally foolish for him to proceed to the question of mental inheritance without a conception of the methods used, and of the general progress made, by the biological sciences in like inquiries. He must at least bear in mind that the days of pangenesis were followed by the days when Weismann challenged the Lamarckian doctrine of use and disuse, these by the days of rapid development in cytology (the science of the cell and its development), and these days, in turn, by the establishment of the science of genetics and of a revised, if tentative, doctrine of heredity. He must also keep in view the general march of events that led up to the rediscovery of Mendel, the attempt to establish "unit characters" and to segregate the elementary factors in descent, the exploitation of sudden or discontinuous variation at the expense of fluctuation, and the wide use of Quetelet's discovery that individual variation follows the law of probability.
But what, you may ask, has psychology to learn from the doctrine of physical inheritance, when bionomic orthodoxy is overgrown with speculation, when evolutionists themselves are asking, fifty years after Darwin, whether the time is yet ripe for a discussion of the origin of species, when they are raising the doubt whether there has yet fallen from the tree of knowledge the apple that shall suggest the discovery of the universal law of inheritance; when Strassburger affirms that the doctrine of heredity must rest upon the study of the cell, and Bateson replies that the student of evolution is "still, as a rule, quite unable to connect cytological changes with any genetic sequence," and that the direct examination of parent and offspring, not of the germinating cell, is the present key to the problem? What can the psychologist hope to learn about method when the biometrician and the follower of Mendel stand at sword's points; the one fighting for measurements, and schemes of distribution, and coefficients of correlation, and the other for segregation, unit characters and laws of dominance and recession?
My reply is, first, that, in spite of his keen enjoyment of the battle, even the observer from the outside can appreciate the invention and application of clever and useful methods and the advancement of knowledge through conflict; and, secondly, that the student of mental inheritance must get at least half of his equipment from the antecedent studies of biology. To be sure, he finds his material within psychology; but he sees that the strict dependence of mental upon physical derivation calls for an alliance with both the biometrician and the student of physiological genetics.
