The reproductive cells in an organism... namely the eggs and sperm. The stem cells which will produce the germ cells become distinguished early in an organism's development. The germ cell is unique in that it conducts meiosis rather than mitoses (if it does not, then cells directly responsible for germ cell formation do) and when mature, is haploid. The egg is totipotent meaning it is capable of forming all of the cell types found in a mature organism. The sperm functions only to fertilize the egg and initiate the process of embryonic development.