Sea Urchin Embryology
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Unfertilized Egg

Fertilized Egg

Zygote cleavage

2 Cell Stage

2 Cell Stage Late

4 Cell Stage

Eight-cell Stage

Sixteen Cell Stage

Thirty-two Cell Stage

Blastula

Blastula -late

Early Gastrula

Gastrula

Gastrula - late

Zona emphasized

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