The tail of the sperm is four times the combined length of the head and body (middle part of the sperm). The tail is formed from cylindrical |fibers| and propels the sperm with a whip-like motion. A sperm may spend several hours in the female before it is able to penetrate and fertilize the egg. Sperm can survive for 24 to 48 hours. When the sperm and egg meet, the head and middle piece of the sperm penetrate the egg, leaving the long tail outside. About 12 hours later the ~zygote~, or fertilized egg, begins to divide.
