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Strongylocentrotus purpuratus (Purple sea urchin)
Colobocentrotus atratus
Echinodiscus tenuissimus
Paracentrotus lividus
Acrosalenia hemicidaroides
Micraster leskei
Illustration[edit]
From "On the Genesis of Species"
Time-lapse video of 16-cell purple urchin embryo