The embryo that does not have an amnion is the human embryo. It is a membrane that covers the embryo when first formed. Mammals, reptiles and birds have this feature.
a fish
the amnion
an amnion
its amnion
the amnion is a fluid-filled sac that will protect the embryo from mechanical shock.
Amnion is the membrane that covers the embryo. Chorion is the membrane that covers the amnion, the yolk sac, and the allantois. The space delimited by the chorion and the amnion is called amniotic cavity and it is filled with aminiotic fluid. The amniotic cavity has the functions of preventing desiccation of the embryo and of protecting it against mechanical shocks.
amnion
There is no such thing as an "ovarian sac". The amnion is a membrane building the "amniotic sac" that surrounds and protects an embryo.
Amniotic sac
Amnion chorion yolksac allantois
frog