Gastrulation continues throughout all sub-divisions of this stage and:
Mid Streak (MS): Tissue at the posterior end of the primitive streak bulges into the proamniotic cavity and forms the posterior amniotic fold.
|Late Streak no bud (LSOB): In the mesoderm of the posterior amniotic fold small cavities coalesce to form a single cavity, the exocoelom.|
| Late Streak early bud (LSEB): The allantoic bud first appears, gastrulation continues and the node becomes visible.
Scale bar in microns.