Tags: Anatomical Structure.
For the alien race in Stephen R. Donaldson’s The Gap Cycle see Amnion (Gap Cycle).The amnion is a membrane that when first formed closely covers the embryo. It fills with fluid the amniotic fluid which causes the amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo. It is a feature of the amniotes which included reptiles birds and mammals. Amphibians and fish are excluded from this group.
