[Initial stages of gonadal differentiation]

Morphological differentiation of gonads results within successive morphogenetic steps beginning with the formation of the undifferentiated gonad, identical in both sexes, through the differentiation of the characteristic gonadal structures, seminiferous tubes in the testis and follicles in the ovary. In this paper, we report recent data on each of these steps and particularly on the origin of somatic gonadal cells. Results from our laboratory are summarized with special emphasis on the relationships between cellular differentiation and morphogenetic processes.