The vas deferens is the canal or duct that passes from the epididymis to the region of the bladder and terminates near its neck by emptying into the seminal vesicles.
"Common Diseases of Farm Animals"
R. A. Craig, D. V. M.
The latter statement does not apply to the mesonephros or epididymis which has moved with the testis, but the latter cannot function without the former, and it may be supposed that the close attachment of the epididymis to the testis had come about in the early Mammalia before the change of position was evolved.
"Hormones and Heredity"
J. T. Cunningham