Amnion
From Wikinfo
The amnion, also called the amniotic sac, is a tough but thin membrane which holds a developing fetus until shortly before birth.
Amphibians do not have amniotic eggs. Mammals, birds, and reptiles do and are called amniotes.
References
- Adapted from the Wikipedia article, "Amnion" http://en.wikipedia.org/wiki/Amnion December 17, 2003
