STAGE 4. Age 2 ¼ hours; length 1.4 - 1.5 mm.

Ext. Crit.: *Advanced eight cell stage*. Dorsal micro- and macromeres usually smaller than ventral ones; dorsal micromeres less pigmente than ventral ones.

Int. Crit.: Third plane of cleavage about 1/3 of animal-vegetative axis. *Pigmented cortical layer and subcortical plasm penetrating over about 1/5 of egg radius along third cleavage furrow*.