In the controversy as to the woman question, appeal has been made to the arbitration of anatomy, in the hope that by that aid a line could be drawn between those characters of males or females that are unalterable because inborn, and those that are acquired. (It was a strange adventure to attempt to decide the differences between the natural endowment of men and women on anatomical results; to suppose that if all other investigation failed to establish the difference, the matter could be settled by a few more grains of brain-weight on the one side.) However, the answer of the anatomists is clear enough, whether it refer to the brain or to any other portion of the body; absolute sexual distinctions between all men on the one side and all women on the other do not exist. Although the skeleton of the hand of most men is different from that of most women yet the sex cannot be determined with certainty either from the skeleton or from an isolated part with its muscles, tendons, skin, blood and nerves. The same is true of the chest, sacrum or skull. And what are we to say of the pelvis, that part of the skeleton in which, if anywhere, striking sexual differences exist? It is almost universally believed that in the one case the pelvis is adapted for the act of parturition, in the other case is not so adapted. And yet the character of the pelvis cannot be taken as an absolute criterion of sex. There are to be found, and the wayfarer knows this as well as the anatomist, many women with narrow male-like pelves and many men with the broad pelves of women. Are we then to make nothing of sexual differences? That would imply, almost, that we could not distinguish between men and women. From what quarter are we to seek help in our problem? The old doctrine is insufficient, and yet we cannot make shift without it. If the received ideas do not suffice, it must be our task to seek out new and better guides. CHAPTER I “MALES” AND “FEMALES” In the widest treatment of most living things, a blunt separation of them into males or females no longer suffices for the known facts. The limitations of these conceptions have been felt more or less by many writers. The first purpose of this work is to make this point clear. I agree with other authors who, in a recent treatment of the facts connected with this subject, have taken as a starting-point what has been established by embryology regarding the existence in human beings, plants, and animals of an embryonic stage neutral as regards sex.