Heredity and environment alike teach this lesson. The child is father to the man, the parents of to-morrow are now being made. The weak should learn early their limitations, the strong should be taught how best to economise their strength. No Eugenist believes in over-emphasis of sexual knowledge, but every Eugenist believes in the absolute importance of early familiarity with the essential information of sex-life. To emphasise this knowledge would mean being guilty of the same _kind_ of error as is at present prevalent. A knowledge of the laws of sex should never be separated from other physiological and moral education, its acquisition should be gradual, its full meaning should be so well prepared for that its physical manifestations in the youth of both sexes would be understood, without the necessity of a sudden jump from abysmal ignorance to overwhelming experience. Co-education, the schooling together of boys and girls until puberty, is a step in the right direction. It familiarises children with each other in quite the best and most innocent manner; it is no more likely to create evil results than the daily life at home of the perfect family of boys and girls meeting under the protection of their own parents. Co-education renders unnecessary that departing into separate schools which is so mysterious in early life. It aims at giving girls the benefit of boys' play, encouraging them in the boys' code of honour, and tending to prepare them for a citizenship they have to share with the boys whom they may even now regard as "chums." For boys the familiarity with girls' ways and girls' characteristics will help them to be courteous without being weak and to lose that shamefaced sex-consciousness which is the opposite to a healthy knowledge of the existence of another sex.