This was an egg set by my broody hen. I pulled it out from under her about day 18, and put it in a makeshift hatcher in my house. It didn't hatch. It was a mutt egg, an EE with most likely a polish roo. I had silkie eggs under the hen, set to hatch a few days later, and I didn't want the two mutt eggs to hatch and have her abandon the silkies, so I brought them in. Neither hatched. One looked ready to hatch, and the yolk was even mostly absorbed, but it didn't make it for some reason. This one died earlier, as it was pretty small. Any idea why this happened?