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Embryology of sea urchin: 8 cells stage
Legend:
1? fertilization membrane (not visible)
2 blastomeres (8x in total)
3 first cleavage plane
4 second cleavage plane
English name: Sea urchin
Scientific name: Psammechinus sp.
Familia: Echinidae
Classis: Echinoidea
Phylum: Echinodermata
Regnum: Animalia
The third cleavage plane is laid perpendicularly to the first two planes (orthogonal; here third cleavage in the same plane as the screen surface). Due to the equal distribution of yolk, all blastomeres have about the same size.
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