Stage 21 (1 day 10 hrs)
6 somite stage (Brain and otic vesicle formation)
Drown by T. Iwamatsu
(Abbr. bc: body cavity)
Stage 21 (1 day 10 hrs) 6 somite stage (Brain and otic vesicle formation):
The optic vesicles differentiate to form the optic cupsand the lenses begin to form. The small otic vesicles appear, but they lack otolith. The three regions of the brain are well- defined, and the neural fold (neurocoele) is seen as a median line along the body. The flat body cavity is recognized on the surface of the yolk sphere bilateral to the mid-brain and hind-brain.