What is the white dot on top of the yolk?

The white dot on top of the yolk is called the germinal disc or blastodisc. This small, white spot is where fertilization occurs if the egg is fertilized, allowing for the development of an embryo. In unfertilized eggs, the germinal disc remains but does not develop into a chick. Its presence indicates the potential for life, even if the egg has not been fertilized.