<Li> <P> Diagram showing later stage of allantoic development with commencing constriction of the yolk - sac . 1 Heart 2 Amniotic cavity 3 Embryo 4 Body - stalk 5 Placental villi 6 Allantois 7 Yolk - sac 8 Chorion </P> </Li> <P> Diagram showing later stage of allantoic development with commencing constriction of the yolk - sac . 1 Heart 2 Amniotic cavity 3 Embryo 4 Body - stalk 5 Placental villi 6 Allantois 7 Yolk - sac 8 Chorion </P> <Li> <P> Diagram illustrating a later stage in the development of the umbilical cord . 1 Placental villi 2 Yolk - sac 3 Umbilical cord 4 Allantois 5 Heart 6 Digestive tube 7 Embryo 8 Amniotic cavity </P> </Li> <P> Diagram illustrating a later stage in the development of the umbilical cord . 1 Placental villi 2 Yolk - sac 3 Umbilical cord 4 Allantois 5 Heart 6 Digestive tube 7 Embryo 8 Amniotic cavity </P>

How does an embryo get food during its development in the egg