"It is incorrect to suppose, as has been held by some theorists, that one testicle give rise to male spermatozoa and the other to female spermatozoa, for both male and female offspring have been produced from the same male parent after one testicle or the other has been removed. The same is true in cases in which either ovary has been removed from the mother; that is, male and female offspring are produced from mothers in whom either ovary has been removed. In like manner, the sex of offspring is shown not to be materially affected by the comparative vigor of the parents; thus, a stronger father than mother does not necessarily produce one sex to the exclusion of the other. These negative decisions are important because they simplify the solution of the problem of sex-determination, by excluding, more or less fully, various causes which have been supposed to operate quite forcibly in deciding the sex of offspring. Some of the more positive agencies that enter into the determination of sex are found (1) in the influence of nutrition upon the embryo during its indifferent stage of sexual development, and (2) in the constitution and general condition of the mother before and during the early stages of pregnancy. These two factors appear to enter more fully than any others in the decision of the sex in offspring, and deserve the greatest consideration. The influence of food in supplying the embryo with nourishment for its development is, perhaps, the most potent of these determining causes." Investigators along the line of theory indicated in the above last quotation, i. e., the theory of sex determination by means of nourishment of the mother and embryo, have presented a volume of reports which demand respectful consideration. The general report may be said to be the discovery that ABUNDANT NOURISHMENT DURING THE PERIOD OF SEXUAL NEUTRALITY TENDS TO PRODUCE FEMALES; WHILE LACK OF ABUNDANT NUTRITION DURING SUCH PERIOD TENDS TO PRODUCE MALES.