Sea urchin embryonic cleavage pattern 

Holoblastic Isolecithal Radial cleavage

Holoblastic: the zygote divides into small cells completely

Isolecithal: the even distribution of yolk

Radial: the division planes are either perpendicular or parallel to the animal-vegetal axis

Fate map and cell lineage of the sea urchin

At 60-cell embryo stage, differentiated cell groups form highly-organized pattern:

Key steps in sea urchin gastrulation

Load 3D Model of a late sea urchin gastrula

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Frog