The idea of sterilization has not yet been very generally understood or accepted, although it is an idea which our civilization urgently needs to assimilate. I think that a large part of the objections to it, often made passionately and eloquently by those from whom one would otherwise have expected a more intelligent attitude, is due to complete ignorance of the facts. Even otherwise instructed persons confuse sterilization with castration. The arguments which to-day in a chance discussion of the subject are always brought forward against sterilization have been, in my experience, only those which apply to castration. To castrate any male is, of course, not only to deprive him of his manhood and thus to injure his personal consciousness, but to remove bodily organs, the loss of which adversely affects his mentality and which will also affect the internal secretions which have a profound influence on his whole organization. I fully endorse the views of the opponents of this process. It is, however, neither necessary to castrate nor is it suggested by those who, like myself, would like to see the sterilization of those totally unfit for parenthood made an immediate possibility, indeed made compulsory. As Dr. Havelock Ellis stated in an article in the _Eugenics Review_, Vol. I, No. 3, October 1909, pp. 203-206, sterilization under proper conditions is a very different and much simpler matter and one which has no deleterious and far reaching effects on the whole system. The operation is trivial, scarcely painful, and does not debar the subject from experiencing all his normal reaction in ordinary union; it only prevents the procreation of children. It has been found in some States of America, and as I know from private correspondents in this country, there are men who would welcome the relief from the ever present anxiety of potential parenthood which they know full well would be ruinous to the future generation. There is also the possibility of sterilization by the direct action of “X” rays. At present sterility is known as an unfortunate danger to those engaged in scientific research with radium, but it might, under control, be wisely used as a painless method of sterilization. This may prove of particular value for women in whom the operation corresponding to the severance of the ducts of the man is more serious. It appears however, not always to be permanent in its effect. In some circumstances this may be an advantage, in others a disadvantage. With reference to the sterilizing effect of “X”-rays, the following quotation from F. H. Marshall, _The Physiology of Reproduction_, 1910, is pertinent:--