So this diagram describes the developing fetus as well as the four extra embryonic membranes as they sit inside the endometrium of the uterus of that female individual, the mother. Now, the actual developing embryo is this structure here. And notice that the coroner is the extra embryonic membrane, is this structure that encloses not only the embryo but also the other three extra embryonic membranes. So the Coryon consists of cells that come from the trophy blast as well as the mesoderm germ layer. And the Coronon functions in two important ways. Firstly, it creates a special fluid we call the coryonic fluid that is located inside the coreonic cavity.