Quote:
Think of a hen's reproductive system as being like an automatic car wash. When your car goes into the car wash, it gets pulled along through the following stages: soap, rinse, wax, dry.
A hen's system drops a follicle once a day from the ovary into the oviduct. The follicle moves down the oviduct and goes through the stages: yolk, egg white (albumen), membranes, shell.
What moves things along is peristalsis - muscle contractions, the same as what moves food down your throat and into your stomach. However, as you have probably noticed, sometimes peristalsis goes backwards. (Blurrrp!)
The same thing happens inside a hen. Occasionally the system kicks into reverse. If this happened in a car wash, your car would go: soap, rinse, wax, soap, rinse, dry. In the case of an egg-inside-an-egg, it gets all the way to the end, then reverses almost all the way back up: yolk, white, membranes, shell, white, membranes, shell.
For me, one of the joys of BYC has been finding out about all the fascinating things that can happen to eggs, and why. Having spent my entire life buying eggs from the store, I really had no idea!
