Cochin egg day 17--still alive but mostly see through?

[Chicat]

Apologies if this is dumb! This is my first time incubating eggs. I have 26 eggs on day 17. 2 silkie, 7 cochin, the rest are mysteries. I candled them today to check the air cells, and all of them are very dark (you can pretty much only see the air cell and some veins) except one. The biggest cochin egg has veins and an embryo, but most of it I can still see through. I honestly thought that it must've been a quitter, but then it began moving.
Pictures:

I left it in the incubator since it's still alive. But is it doomed? Or is this normal? Is it because it's a bigger egg than the other cochins?

 

[Poultrykeeper12]

It is completely normal! The embryo looks very healthy. It may be developing slower then the others, which could lead to it hatching later then it's supposed to. Otherwise it looks very well. Good luck! And happy hatching.

 

[CindyinSD]

I would just wait and see. It could be in a cooler spot in the incubator. I have a duck egg like that right now, only much smaller embryo than yours. I've been rotating the eggs around the incubator, so I suspect there's just something amiss. But I'll leave it in.

Some people call the hatch and discard any eggs that haven't hatched within the 20-22 day time period as stragglers often don't do well. A lot depends on your personal philosophy and goals. If you are very tender toward individual animals you may want to do all you can for the survival of each individual. If you have a more pragmatic approach, you may feel it's unkind to engage in heroic measures to save a chick on the edge, and choose to turn off the incubator. I would leave it in and give it a chance, but not intervene if it doesn't hatch on its own or on time.