The amnion, option 1, is indeed a protective membrane that surrounds and protects the developing embryo from desiccation (or drying out) during gestation. This membranous sac fills with amniotic fluid and essentially acts as a cushion to protect the fetus.

Option 2, the allantois, plays a role in respiration and excretion in the embryo, but it does not directly safeguard against desiccation. Its main function is as a conduit for waste from the embryo.

Option 3, the chorion, is an outer membrane that encloses the embryo and other membranes. It contributes to the formation of the placenta but does not specifically guard against desiccation.

Option 4, the yolk sac, is a membrane that is connected with the embryo`s midgut and provides nourishment in early stages of development in some species, but it doesn`t protect from desiccation.

So, while all four options are important to embryonic development, only the amnion plays a role in protecting the embryo from desiccation.