somatopleure

The mesoblast of the somatopleure is continued into the opaque area as a single layer of spindle-shaped cells.

At the junction of somatopleure and splanchnopleure they are more rounded than elsewhere.

In this way the embryo becomes surrounded by a series of folds of thin somatopleure, which form a continuous wall all round it.

This second fold gives rise to the amnion, and is limited entirely to the somatopleure.

The part of the somatopleure, which grows round it, is to be regarded as a modified portion of the ventral wall of the body.