|The most obvious distinguishing features are the deepening
of the lens pit, with a narrowing of it's outer pore-like opening,
and the first appearence of the physiological umbilical hernia. The
1st branchial arch is conspicuously divided into it maxillary and
mandibular components. There is advanced development of the brain
tube and the tail elongates and thins.
Absent: nasal pits.
All scale bars in microns.