#1.34
Apart from the yolk and white, only two things are originally missing in
order for an embryo to develop: warmth and oxygen. Heat will come from the
hen sitting on the eggs, keeping them warm, in what is known as incubation.
But, what about the oxygen and where does it come from? Eggshells have
thousands of tiny holes in the shell that allow the embryo to breathe. A hen's