The Fitch & Denenberg target article focuses almost exclusively on short gestation mammals, which differ substantially from long-gestation mammals in the timing and type of hormonal contribution to their sexual differentiation. Conclusions regarding the role of ovaries in female sexual differentiation may accordingly apply to only a limited number of species. Specific criticisms of the organizational effects of hormones stem from an incomplete reading of the original literature. The mechanisms proposed in this target article reflect an extension of the principle of hormonal organization, not a revolutionary restructuring.