The yolk is basically a carrier of genetic information (after fertilization, of course - it is such a tan red to brown spot on the surface of the yolk). The protein is basically used to nourish the embryo. so much about the egg. the hens themselves cannot reproduce, they need a rooster to fertilize their eggs. if we do not have time to loot those eggs and throw them in the pan, then the hen warms them with its body heat (sitting on them), a new individual begins to develop from the gamete (that spot) - chicken (young domestic chicken, hen or rooster). (tuxedo)