Great idea, thanks !! Here is a pic of the veins I'm referring to !
Looks like vessels, not allantois, which is the sac that holds white urates. I’m just the constant stick in the mud here, but again, I’d wait and be careful that he doesn’t try to kick out prematurely. I would guess that those prominent vessels mean that he’s still absorbing yolk...Great idea, thanks !! Here is a pic of the veins I'm referring to !