REASONS FOR NOT MIXING OF WHITE EMBRYO AND THE YOLK IN THE EGG:
The white embryo and the yolk have equal density. So they don’t mix with each other. Further, around the yolk, there is a membrane packing. Additionally, there is ‘Chalazas’ preventing the movement of the yolk, on its both sides. When the egg is broken, this fiber is torn and the membrane is snapped. Only after that the mixing of the white embryo and the yolk is possible.