http://www.digitaljournal.com/article/326077

Woman finds double egg, egg within egg

Posted Jun 5, 2012 by Leigh Goessl
A Texas woman made an interesting discovery in her chicken coop yesterday when she found a massive-sized egg inside one of the nests.
screengrab of an example of an egg within an egg
screengrab of an example of an egg within an egg
New Scientist
Cookie Smith has three chickens on her farm. Each day she collects the eggs from the hens, but that morning held a surprise.
According to the Abilene Reporter News, Smith said, "I just died laughing when I saw it. There in the nest was a "mutant super egg." She described the egg as being the same shape and color of the usual eggs, but quite a bit larger.
The egg was described as being about an inch longer than normal eggs, but three times the weight, it weighed about five ounces (145 grams). Smith said she took a few photos and then placed the egg in the refrigerator, unsure what to do with it. She took the photos to work and showed her coworkers.
Her colleagues urged her to call the news because it was so unusual. Abilene News came to her house to take some photographs.
An unusually large egg does occur sometimes, but what Smith discovered when she cracked this egg open was much rarer. The egg contained inside what was expected when one would ordinarily crack open an egg, but in addition was a second normal sized egg (weighing 55 grams) within the large egg. Not a double yolk egg, but an actual regular sized egg within the larger one.
In the New Scientist blog, in 2008 an individual who experienced this same phenomenon wrote in and inquired about an egg within an egg, generating responses.
One of the responders, Douglas Russell, Curator, bird group, Department of Zoology, The Natural History Museum, Tring, Hertfordshire, UK, elaborates this occurrence in this video:
What generally happens, is that as the egg is developing and being pushed down the oviduct, a series of abnormal contractions can occur which can push a developing egg back up the oviduct. What happens is one egg will be surrounded by another egg.
Russell describes this as a "relatively rare" occurrence.
In case you're wondering what Smith cooked with the egg, she opted not to eat it. Noting the two eggs may be "perfectly OK" to eat, she was afraid to take a chance.
"No way. It may be fine, but it's a mutant egg," she said. "Its DNA may be messed up or something."
Smith and her husband, Leonard, are not sure which of their three hens laid the remarkable egg.