The human male gamete, the sperm has to flow through the female reproductive tract to reach the fallopian tube, where it can fuse with the ovum. Thus, it requires an organ for rapid and efficient motility for transportation. The tail provides this function. The female gamete or the ovum has to travel very little distance, in which it is helped by the ovary and fallopian tube. Thus, it doesn’t require any tail.

Thus, only the male gamete has a tail.