STAGE 7. Age 4 h.; length 1.4 - 1.5 mm.

Ext. Crit.:*Large-cell blastula stage*. *In animal view about 10 micrometers along meridian*.

Int. Crit.: *Tangential cleavage; formation of double-layered embryos*. Except for rather sharp boundary between outer equatorial and vegetative blastomeres, transition between various regions still very gradual. *Pregastrulation movements noticeable for the first time*: slight epibolic extension of animal and equatorial areas and beginning of ascendance of plasm along cleavage furrows near vegetative pole.