different stages of development

[Dan K]

This is my first attempt at tumbling. Yesterday I stripped my female and poured all of the fry (she had been holding 8 days) into the tumbler. There appeared to be one dud egg but I didn't pull it out. Today, what looked yesterday like an infertile egg has sprouted a tail and eyes are forming. The rest of the batch is so far ahead in development. Is it common that a few eggs develop later or slower than the rest? 

[Ron]

Is it common that a few eggs develop later or slower than the rest?

Yes, it makes perfect sense in nature. IMO the best non-fish example would be birds. They also don't all hatch at the same time.