.Stages of Growth
Here are a few pictures of what it looks like inside the duck egg during the 28 day period.

Day Four

After four days you can see the eye. It is a dark spot. The sac is filled with a watery fluid. Its nose, legs and wings are starting to develop too. The duck is inside the "amniotic sac", which protects the embryo.

Day Seven

The embryo has been kept warm for one week now. You can still
see the eye (far left), and now you can see the blood vessels
attached to the embryo, which is attached to the yolk. Although you
can not see it, there are the beginnings of a brain, a heart, ears, a
beak and a stomach and a tongue.

Day Eleven

It looks like a duck now. You can see its beak and its wings. It is about 11 days old. You can still see it's big eye! If you candled the egg, you might see it's body moving around inside the sac.

Day Sixteen

Now it is about 16 days old. It is starting to grow feathers. It has claws and toes. It is getting in the right position for breaking open the shell.

Day Twenty-four

The duck is now 25 days old. It is getting fatter and fatter. It begins to suck up the yolk sac, so it can have enough strength to kick out of the shell. It is pretty squished inside the egg.

Day Twenty-eight
On the 28th day, the duck starts to pip inside the egg. It breaks into the air sac, and starts to peck away at the shell. This can take a long time because the duck has to rest between. When the duck has worked it's way around, it turns its body and pushes the top of the shell off. Then it kicks off the rest of it's shell.