The appendix of the epididymis (or pedunculated hydatid) is a small stalked appendage (sometimes duplicated) on the head of the epididymis. It is usually regarded as a detached efferent duct.This structure is derived from the Wolffian duct (Mesonephric Duct) as opposed to the appendix testis which is derived from the Müllerian duct (Paramesonephric Duct) remnant.