But we all of us realize that it is not the facts of birth, but the facts of the origination of life, that form the perennial source of obscene talk, and often of obscene action, among boys; and it is in explaining these, without violating those instincts of reserve and modesty with which nature herself surrounds the whole subject, that what often seems an insuperable difficulty arises.

Yet these functions are, and must be, the very shrine of a body which is a temple of the Lord and Giver of life; and on the face of things, therefore, there must be some method of conveying pure knowledge to the opening mind with regard to them.

The difficulty must be with ourselves, and not in the very nature of things themselves.
Has it not been created in a great measure by a wrong method?
We begin with human life instead of ending with it; we isolate it from a great system to which it belongs, and treat what is "the roof and crown of things" as a roof that tops no fair edifice, and is therefore anomalous; as a crown that rests on a head which has been severed from its body, and is therefore unmeaning.

We obstinately refuse to live--to quote Goethe's words again--not only "in the beautiful and the good," but also "in the whole," which is equally necessary for a well-ordered life.

What it seems to me we need is to teach the facts of life-giving, or, in other words, of sex, as a great, wide, open-air law, running right through animated creation, an ever-ascending progression forming a golden ladder leading up to man.
In explaining the facts of reproduction, I would therefore suggest that you should begin with the lowest rung of the ladder, the simplest organisms, such as the amoeba or the volvox.