Yolkless egg

I had to look that up. Here is what Wikipedia says about yolkless eggs:

Yolkless eggs

Eggs without yolk are called "dwarf" or "wind" eggs.^[8] Such an egg is most often a pullet's first effort, produced before her laying mechanism is fully ready. In a mature hen, a wind egg is unlikely, but can occur if a bit of reproductive tissue breaks away, stimulating the egg producing glands to treat it like a yolk and wrap it in albumen, membranes and a shell as it travels through the egg tube. This will occur if, instead of a yolk, the egg contains a small particle of grayish tissue. An archaic term for a no yolk egg is a "cock" egg.^[9] Since they contained no yolk and therefore can't hatch, it was traditionally believed that these eggs were laid by roosters.^{[citation needed]} This type of egg occurs in many varieties of fowl. They have been found in chickens, both standard and bantams, guineas and coturnix quail. See Cock egg.