Origin of müllerian duct and its later developmental changes in relation to wolffian duct in bovine fetuses.

At the 1.6-1.8 cm stages in both male and female bovine fetuses, the anlage of the Müllerian duct was first observed as an elevation of mesothelium on the cranial tip of the mesonephros. The duct extended toward the urogenital sinus in parallel with the Wolffian duct. Its caudal end was solid and was fused with the Wolffian duct at about the level of the middle of the gonadal anlage. Thereafter, the Müllerian duct became gradually independent of the Wolffian duct throughout its whole length. Therefore, it may be that the main part of the Müllerian duct is established by budding from the Wolffian duct. At the 4.3-4.5 cm stages the male Müllerian duct began to degenerate and the female one continued to grow. This suggests that the male Müllerian duct is affected by the Müllerian inhibiting substance at these stages. At the 12.0 cm stage, the female Wolffian duct disappeared. The male Wolffian duct was also much reduced in diameter at this stage, but began to grow again from the 14 cm stage onward.