To solve this problem, we need to determine the embryonic origin of the amnion in mammals.$\newline$The amnion is a membrane that forms a protective sac around the embryo, filled with amniotic fluid.$\newline$Let's analyze the embryonic layers involved in its formation:$\newline \bullet$The amnion is derived from two germ layers: the ectoderm and the mesoderm.$\newline \bullet$The ectoderm forms the inner lining of the amnion, while the mesoderm contributes to the outer layer.$\newline$Therefore, the correct answer is that the amnion is derived from the ectoderm and mesoderm.$\newline$This corresponds to Option 3: ectoderm and mesoderm.