Zygote

1-cell stage (0 h): The chorion swells and lifts away from the newly fertilized egg (Fig. 3A). Fertilization also activates cytoplasmic movements, easily evident within about 10 minutes. Non-yolky cytoplasm begins to stream towards the animal pole, segregating the blastodisc from the clearer yolk granule-rich vegetal cytoplasm (Fig. 3B). This segregation continues during early cleavage stages.