What I have attempted to do in this talk is to define and trace the biological origins of an individual's predispositions — those predispositions which are a function of his or her sex. I have not even ouched upon the marmer in which the social environment may accentuate, attenuate or even negate such predispositions. The primary objective of my efforts so far is an understunding of how, in the process of becoming boy or girl, man or woman, an individual is constrained in certain ways, primed in others and blased to accept or reject the manifold impresses of society.