The yellow eggs I had laid ALL showed signs of veins, which I understood to mean they were fertilized eggs... however they all died, which leads me to believe that the three day period with high heat for the mother while gravid interrupted or damaged something in the eggs, so that when they reached ten to twelve days post laying they started to die.
I think that a clutch of 15 slugs would have been easier to take than a clutch of 15 eggs which, albeit yellow, developed strong veins, and THEN started to die.
Good luck with yours! They look nice. I'm sure mine was a fluke of the Air-Conditioning Gods!
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~Sasheena