only one way to get them out, by preventing the reproduction. All social welfare work is merely education of the germs of traits; it does not provide such germs. In the absence of the germs the traits can not develop. On the other hand, it is possible with difficulty, if possible at all, by means of the strongest repressive measures merely, to prevent the development of undesirable hereditary traits. Society can treat the delinquent individual more reasonably, more effectively, and more humanely, if it knows the 'past performance' of his germ-plasm."
In addition to their importance to society, a knowledge of the traits of a pedigree has a great direct importance to the individual; one of the most valuable things to be learned from that knowledge is the answer to the question, "What shall a boy or girl do? What career shall one lay out for one's children?" A knowledge of the child's inborn nature, such as can be had only through study of his ancestry, will guide those who have his education in hand, and will further guide those who decide, or help the child decide, what work to take up in life. This helps to put the problem of vocational guidance on a sound basis,—the basis of the individual's inherent aptitudes.
Not too much must be expected from vocational guidance at the present time, but in the case of traits that are inherited, it is a fair inference that a child is more likely to be highly endowed with a trait which both parents possess, than with one that only one parent possesses. "Among the traits which have been said to occur in some such direct hereditary way," H. L. Hollingworth47 observes, "or as the result of unexplained mutation or deviation from type, are: mathematical aptitude, ability in drawing,48 musical composition,49