Ejaculatory system. 1866 illustrations showing details of the organs involved in the production of semen. Fig. 1: the seminal vesicles (oval, left and right), vas deferens (tubes, top) and ejaculatory duct (small oval hole, lower centre). Fig. 2: cross-section through one of the vas deferens (tube, left) and seminal vesicles (oval, right). Fig. 3: cross-section through showing the internal surface of one of the vas deferens. The seminal vesicles secrete a significant proportion of the fluid that ultimately becomes semen. The vas deferens transport sperm from the epididymis of the testes to the ejaculatory ducts in anticipation of ejaculation. The two ejaculatory ducts are formed by the union of the vas deferens with the duct of the seminal vesicles.