Except for the most cranial portion, the appendix epididymis, the mesonephric ducts persist and form the main genital ducts. Immediately below the entrance of the efferent ductules, the mesonephric ducts elongate and become highly convoluted, forming the ductus epididymis. From the tail of the epididymis to the outbudding of the seminal vesicle, the mesonephric ducts obtain a thick muscular coat and form the ductus deferens. The region of the ducts beyond the seminal vesicles is the ejaculatory duct. Except for a small portion at their cranial ends, the appendix testis, the paramesonephric ducts in the male degenerate.