Sea urchin
For decades, the sea urchin embryo has been used to establish the chromosome theory of heredity, the description of centrosomes, parthenogenesis, and fertilization. Research work during the last 30 years established such important phenomena as stable mRNA and translational control, isolation and characterization of the mitotic apparatus, and the realization that the major structural proteins of the mitotic apparatus are microtubules. Sea urchin studies provided the first evidence of actin in nonmuscle cells.