Bull sperm. Coloured transmission electron micrograph (TEM) of bull sperm (spermatozoa). Sperm are the motile male sex cells. Each sperm is broadly divided into a pear-shaped head, neck and a long, thin tail. The head contains the genetic material of the male needed to fertilize the female egg (ovum). The head is joined to the tail by a short neck. The sperm's tail enables it to swim by whiplash movements, an action that propels it to reach the ovum. Magnification: x1,200 at 6x7cm size. x4000 at 8x10"~PORTRAIT"