This type of egg occurs in many varieties of fowl, including chickens (both standard and bantams), guineafowl, and Japanese (Coturnix) quail.
[citation needed] Since they contain no yolk and therefore cannot hatch, yolkless eggs were traditionally believed to be laid by cocks.
[3] This gave rise to the myth that when a cock's egg was hatched, it would produce a cockatrice, a fearsome serpent which could kill with its evil stare.
According to the superstition, this could be prevented by throwing the egg over the family dwelling so it smashed on the other side without touching the roof.
This may be due to too much albumen, or it may function to separate viable eggs from each other and thereby improve gas exchange.