Many phenomena, amongst which may be noticed specially experiments on the regeneration of lost parts and investigations into the chemical differences between the corresponding tissues of nearly allied animals, have led the investigators to whom I have just referred to conceive the existence of an “Idioplasm,” which is the bearer of the specific characters, and which exists in all the cells of a multi-cellular animal, quite apart from the purposes of reproduction. In a similar fashion I have been led to the conception of an “Arrhenoplasm” (male plasm) and a “Thelyplasm” (female plasm) as the two modes in which the idioplasm of every bisexual organism may appear, and which are to be considered, because of reasons which I shall explain, as ideal conditions between which the actual conditions always lie. Actually existing protoplasm is to be thought of as moving from an ideal arrhenoplasm through a real or imaginary indifferent condition (true hermaphroditism) towards a protoplasm that approaches, but never actually reaches, an ideal thelyplasm. This conception brings to a point what I have been trying to say. I apologise for the new terms, but they are more than devices to call attention to a new idea. The proof that every single organ, and further, that every single cell possesses a sexuality lying somewhere between arrhenoplasm and thelyplasm, and further, that every cell received an original sexual endowment definite in kind and degree, is to be found in the fact that even in the same organism the different cells do not always possess their sexuality identical in kind and degree. In fact each cell of a body neither contains the same proportion of M and W nor is at the same approximation to arrhenoplasm or thelyplasm; similar cells of the same body may indeed lie on different sides of the sexually neutral point. If, instead of writing “masculinity” and “femininity” at length, we choose signs to express these, and without any malicious intention choose the positive sign (+) for M and the negative (-) for W, then our proposition may be expressed as follows: The sexuality of the different cells of the same organism differs not only in absolute quantity but is to be expressed by a different sign. There are many men with a poor growth of beard and a weak muscular development who are otherwise typically males; and so also many women with badly developed breasts are otherwise typically womanly. There are womanish men with strong beards and masculine women with abnormally short hair who none the less possess well-developed breasts and broad pelves. I know several men who have the upper part of the thigh of a female with a normally male under part, and some with the right hip of a male and the left of a female. In most cases these local variations of the sexual character affect both sides of the body, although of course it is only in ideal bodies that there is complete symmetry about the middle line. The degree to which sexuality