The eggs can't develop without the warmth provided by the hen. But a single hen can't effectively cover 25 eggs, and as she instinctively rotates the eggs in and out of the center of the clutch, I expect that the eggs haven't been kept warm enough to develop. You could take one or two off the pile and crack them open to see (careful, do it over a trash can because partially developed chicks can be kind of gross looking, and if they've gone bad they'll stink!).

Here is a link that might be useful: My blog: Life at Busy Solitude Farm

Wow there is a lot to consider in this.... I hope you did not crack any of the eggs yet, lol....that can be really bad!!

First if they are all her eggs, there is no way that all of them could even be viable since it would take her at the very least 25 days to lay 25 eggs... not likely, lol.... since it only takes 21 days to incubate them. In the time it took her to lay a clutch, the first eggs were aging and by now could be quite undesirable, lol... you could easily use a flash light and a TP tube to candle a few.... lots of images on line to show you what to look for....

And you said, she had been gone for weeks? Once again, only 21 days needed for hatching, so three weeks tops and the job is done.... all in all it is probably best that you chased her off the nest so that you can gather and dispose of them before they go popping and bursting from inner pressure......that odor will kill ya, lol..... try candling all the eggs.... take a peek here.....http://shilala.homestead.com/candling.html or http://ucanr.org/freepubs/docs/8134.pdf.........good luck

I've found that if the clutch is that big, it won't be totally successful. I don't think there is enough chicken butt to cover that many and they do need heat to be viable. I have had a hen hatch out 10 chicks before but was sitting on a great many more. I pitched them and after examination, discovered that nearly all had been fertile at some point. I'm not sure if she decided "enough already" and wanted to care for the ones she had or if they just didn't get the turning and heat the rest of them did. I would pitch the eggs for sure. Lori