In order to determine the best age at which to marry, we must be guided by certain fixed standards. We must find out from statistics the average age of the parents of the best babies. We must determine and analyse the qualifications of what constitutes the "best" babies, according to the eugenic ideal. We should give heed to the fixity of temperamental characteristics in order to determine their adaptability to conditions that prevail at certain ages. We should select an age in advance of the period at which science has determined individuals to have outlived any hereditary tendencies. We have abundant proof that the best babies are born of parents between the twenty-third and the twenty-sixth years. We know also that the age which responds, with the fullest degree of plasticity, to temperamental characteristics, is in the early twenties. We know, likewise, that inherited tendencies may be said to have been outlived at or about the twenty-second year. The ideal marrying age, therefore, is, for both male and female, approximately the twenty-third year. The physical, mental and moral development of both men and women, at this period, evidence a high degree of adaptability, and are responsive to the institution of marriage. Their hereditary traits, if any previously existed, assume a dormant form at this age. They have cultivated the temperamental qualities which they will retain, with few modifications, throughout life. On the other hand, their dispositions are responsive to reason, and are capable of readjustment. Their temperamental characteristics are plastic, and under favorable conditions it is possible for both to evidence a degree of sympathy and toleration that bespeaks future harmony and success. No marriage can result in mutual happiness and success if one of the participants is temperamentally incapable of changing his or her convictions. One of the fundamental essentials to peace in the home is the quality of adaptation to circumstances, and no other virtue will be called into existence oftener than this quality. At this age, a man is eager to contribute to the contentment and happiness of his partner, even if it is necessary to sacrifice his own whims and opinions, and a woman, at this period, is temperamentally so constituted that she will respond to the same impulses.