The rapidly growing interest in Eugenics, and the scientific consideration of the world-wide decline in the birth-rate have drawn attention to the study of the eugenic factors which determine the production of high ability in offspring. Many distinguished investigators have conducted long and exhaustive investigations for the purpose of ascertaining and summarizing all possible biological data concerning the parentage and birth of the most notable persons born in European countries, and to a lesser extent in America. The investigations are now acquiring a fresh importance, because, while it is becoming recognized that we are gaining a control over the conditions of birth, the production of children has itself gained an importance. The world is no longer to be bombarded by an exuberant stream of babies, good, bad, and indifferent in quality, with mankind to look on calmly at the struggle for existence among them. Whether we like it or not, the quantity is steadily diminishing, and the question of quality is beginning to assume a supreme significance. The question then is being anxiously asked: "What are the conditions which assure the finest quality in our children?" A German scientist, Dr. Vaerting, of Berlin, published just before the War a treatise on the subject of the most favorable age in parents for the production of offspring of ability. He treated the question in an entirely new spirit, not merely as a matter of academic discussion, but rather as a practical matter of vital importance to the welfare of modern society. He starts by asserting that "our century has been called the century of the child," and that for the child all manner of rights are now being claimed. But, he wisely adds, there is seldom considered the prime right of all the child's rights, i. e., the right of the child to the best ability and capacity for efficiency that his parents are able to transmit to him. The good doctor adds that this right is the root of all children's rights; and that when the mysteries of procreation have been so far revealed as to enable this right to be won, we shall, at the same time renew the spiritual aspect of the nations. The writer referred to decided that the most easily ascertainable and measurable factor in the production of ability, and efficiency in offspring, and a factor of the greatest significance, is the age of the parents at the child's birth. He investigated a number of cases of men of ability and efficiency, along these lines, and made a careful summary of his results. Some of his results are somewhat startling, and may possibly require the corroboration of other investigators before they can be accepted as authoritative; but they are worthy of being carefully considered at the present time, pending such further investigation.