462 THE POPULAR SCIENCE MONTHLY 



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 first- 

 hand 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 in- 

 heritance 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 "VVeismann 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 estab- 

 lishment of the science of genetics and of a revised, if tentative, doc- 

 trine of heredity. He must also keep in view the general march of 

 events that led up to the rediscovery of Mendel, the attempt to estab- 

 lish " 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 doc- 

 trine 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 con- 

 nect 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 ps3 r chologist 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 segrega- 

 tion, 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 psychol- 

 ogy; 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. 



