Temperature: It has to be between 99.5oF and 100.5oF or it could come late or early hatching. Humidity:If the humidity is to low the chicks could have trouble hatching.
Turning the eggs:Always wash hands before and after turning the eggs.Make sure eggs are marked with pencil. Fresh air:Don't use markers to label your eggs.Don't use strong chemicals,or cleaning supplies near the eggs.
The embryos on day 18 all the albumen is gone and it´s just the yolk
shell mem. :This membrane helps keep polluted air out of the egg.
yolk sac:The embryo has a 21 day food source of yolk.
Egg tooth:The egg tooth is a temporary organ because it falls off 2-3 days after it hatches
The egg tooth starts developing on the 2-3 day it´s an embryo.
Day 21 they pip through the air cell and take their first breath as a chick.