"I am, therefore, a young girl whose sensations are neither cold nor perverse, and I am always rejoiced, in reading your book, to see with what truth you describe our sexual impressions. Those who maintain that we feel in this way the same as men make me smile. In your book ("Hygiene of Marriage," p. 479) you say that the idea of marriage awakens in a normal young girl a kind of anguish and disgust, and that this feeling disappears as soon as she has found some one whom she loves. This is extremely true and well observed. I am in complete agreement with a friend with whom I have often discussed your book; we young girls are very little attracted by the purely sexual side of marriage, and we should prefer to see children come into the world by some other way than that ordained by Nature. This will, perhaps, make you laugh. However, I think you will understand my feelings. "When I had finished reading your book I became absolutely tranquil, and my ideas were enlightened. It goes without saying that it is no longer possible for me to be ingenuous, but I should like to know what one gains by such naivety. It is very easy to be innocent when one knows nothing, and this is of no account. I never thought for a moment to find your book immoral, and that is why I do not think you have done me any harm. Excuse me for having written at such length, but I could not abbreviate when dealing with such a serious question." The author of this letter has, at my request, authorized me to publish it anonymously. I think that the candor, the loyalty and the maturity of judgment of the sentiments expressed by this young girl are of much more value and are much more healthy than all the prudishness and false shame of our conventional morality. DR. A. FOREL. Chigny près Morges (Suisse). CONTENTS CHAPTER I PAGE The reproduction of living beings--History of the germ-- Cell-division--Parthenogenesis--Conjugation--Mneme--Embryonic development--Difference of sexes--Castration--Hermaphrodism-- Heredity--Blastophthoria 6 CHAPTER II The evolution or descent of living beings 39 CHAPTER III Natural conditions of mechanism of human coitus--Pregnancy-- Correlative sexual characters 49 CHAPTER IV The sexual appetite in man and woman--Flirtation 72 CHAPTER V