[Pavel Chaloupka]

Yeah but if they die becouse of high pH or for some other reason, you still will not know if they were fertilized or not. Becouse most of the fertilized eggs that die will die during the very first stages of developement. So if you isolate the clutch there is no guarantee you get information you wanted to get if the eggs do not develop. Just comes to my mind. Are the eggs so whitish that the perivitelline space is not visible? And if yes, could it be visible under strong light? If you are planning to take out the eggs anyways, could you have a look? Than you clearly know if the cluch is fertilized. On such big eggs it should be even visible without magnifying glass. If its not visbble becouse of the eggs coloration, than using some dye like methylen blue could help, as it would penetrate unfertilized eggs much more than fertilized ones. But you would have to check with some fertilized eggs first to be able to tell the difference.