Yolk sac's are yellow/orange with veins. Usually green sac's are where the metabolic wastes go while the chick is developing in the egg. A poop sack of sorts. The true name escapes me at this late hour. In my blurry eyed state, that looks like the chick has been dead for a bit and the wastes from the poop sack has spread all around inside the chick and thus yolk sac, becaues dead tissue isn't very good at keeping things where they need to be.
For stages of chicks on different days of development, google Hamburger and Hamilton "A series of normal stages in the development of the chick embryo" 1951. If you can get your hands on the orignial or reprint of the article, it defines each stage of development and describes what happens.
For stages of chicks on different days of development, google Hamburger and Hamilton "A series of normal stages in the development of the chick embryo" 1951. If you can get your hands on the orignial or reprint of the article, it defines each stage of development and describes what happens.
