hens laying meaty chunks!

[fen not fen]

Collecting the eggs yesterday from my mixed flock of bovans and lohmanns I found something odd in one of the nestboxes. It looked like a piece of smoked tofu, but when broken open was meaty inside, with some watery stuff. It was about the size of an egg but not egg shaped. It smelt fairly neutral, with only a slightly offensive smell. What is it? There is no cockerel with the hens.