Sperm made in the testis go into the head ("caput") of the epididymis, go through the body ("corpus") and stop at the tail ("cauda"), where they are stored. When sperm are first made and travel to the head, they are not yet ready to be ejaculated. They cannot swim or fertilize an egg. By the time they reach the tail, the sperm can fertilize an egg. The sperm are transferred to the Seminal visicle through the vas deferens. The sperm can not swim yet, so muscle contractions push the sperm to the seminal vesicle where final development is finished. . 