Induction of testicular differentiation in the fetal mouse ovary by transplantation into adult male mice. 
Mouse ovarian primordia on the 12th or 13th day of gestation frequently developed testicular structures in addition to ovarian structures by the 14th day after transplantation into a site beneath the kidney capsules of adult male mice.  Electron microscopic examination of the testicular portion of ovotestes revealed all types of testicular somatic cells, i.e., Sertoli, myoid, and Leydig cells, but not spermatogenic cells.  On the other hand, after transplantation into adult female mice ovarian grafts developed only ovarian structures.  We conclude that female gonadal somatic cells differentiate into testicular components in a male host environment.