It takes 21 days (three weeks) for hen eggs to hatch

[Muhaba]

Someone obviously lied when they said:

One does not need to a scholar to be clever. Here is now you do it. Embryos nearly all look alike. Tadpole, chicken, human, and cow.
If you have one hen, she will lays many eggs at once. Let her incubate all her eggs at once. Steal one after the first week and crack it, you will see it looks like a clot. Steal another egg the second week, you will see a leech. Wait a week or two, steal a third egg and you will see it looks like chew substance. You see the sequence, you will see the embryo of the chicken developing. Do this again and again, carefully recording the time the egg was incubated and the time you cracked.

[Muezzin]

That person really needs to introduce him or herself to Google Image Search:

Down with killing innocent foetus-chicks!

You can't even make an omlette out of those eggs.

[Yanal]

Poor creatures.