The facts observed and recorded by others assisted me to advance so far onthe trodden path that I made an effort to snatch a secret from Nature.What I succeeded in obtaining, though small, induced me to set forth in thefollowing pages the perhaps not unimportant results.The labor was long, and engaged my attention for years. And yet, amidst mycontinuous labors in the province of Embryology, it remained all the time amatter of secondary importance, my principal attention being engaged by farmore extensive studies.My desire is to stimulate others to wider observation. May the facts which Ihere discuss prove of utility, and encourage further studies in this direction withthe assistance of modern science.If we are not in a position to control the processes of Nature, we cannevertheless exercise over them a more or less effective influence, so as toobtain such results as are possible.Whatsoever the question may be that we propose to discuss, it is sometimesvery difficult to reach any answer. And yet, when experience and diligence havehelped us over the difficulties, we succeed at last in reaching the answer desired.The difficulties assume much less formidable shapes when an individual issatisfied with shaking his head and regarding the whole affair with mistrust. Inthat way the inexperienced and lazy are at once able to launch their viewswithout further trouble. They believe or they disbelieve; and they like to havetheir say. Any one can in this way easily win himself a place amongst those whohave written on a topic. The man who desires to obtain a lasting place takes onhis shoulders heavier responsibilities.This book contains but a portion of the vast and wide-reaching literaturedealing with the subject in hand. That literature extends back to the date ofman’s earliest intellectual labors. The observations that have been recorded byothers are here followed by methods of investigation, and by considerationswhich may serve to elucidate the facts. In conclusion, a section has beendedicated to the methods which I recommend for the artificial influencing of sex.Some particular experiments are subjoined.May my little book, then, go out into the world and make known my views,which are founded exclusively upon facts.