The egg of any bird is a more complicated production than superficial consideration would lead us to believe. The yellow or yolk of the egg is formed within the bird’s reproductive organ or ovary. The yellow breaks out of the ovary, enters the upper end of the reproductive tract or oviduct, where the white is added; then travels down to the lower part of the tube where the membranes and shell are applied around the yellow and white. The egg then is ready to be laid an accomplishment that the hen announces to the world with loud cacklings.
Only a small part of the egg is living material that will develop into a young bird or chicken. This is the small whitish spot in the yellow, which can easily be seen if a hen’s egg is removed from the shell. During incubation the young chicken or bird is formed from the small living part of the egg, while the yolk and white serve as food material for the developing embryo. In fertilized eggs-and most eggs are fertilized unless roosters and hens are separated-a certain amount of development occurs before the egg is laid. Therefore, when one breakfasts upon a platter of eggs, one is in reality eating embryonic chickens.