Final answer:
The inferior portion of the epididymis from which the ductus (vas) deferens emerges and is responsible for the maturation and transport of sperm is called the tail.
Step-by-step explanation:
The inferior portion of the epididymis, from which the ductus (vas) deferens emerges, is called the tail. The epididymis is divided into three parts: the head, the body, and the tail. The head is located on top of the testis, the body drapes down the side of the testis, while the tail is the part that joins with the vas deferens near the bottom of the testis. The epididymis functions to mature the sperm, and the vas deferens transports the mature sperm during ejaculation.