11. Most starfish embryos hatch at the blastula stage. 12. In " Xenopus " embryos, the blastula is composed of three different regions. 13. Within the blastula , inner blastomeres are generally non-polar while epithelial cells demonstrate polarity. 14. Named by William Ballard, the pharyngula stage follows the blastula , gastrula and neurula stages. 15. In sponges, blastula larvae swim to a new location and develop into a new sponge. 16. By manipulating the cell signals during the blastula stage of development, various tissues can be formed. 17. Cell-cell interactions mediated by E-cadherin are crucial to blastula formation in many animals. 18. They showed that uncommitted cells of the zebrafish blastula animal pole into a well-developed embryo. 19. Von Baer studied the embryonic development of animals, discovering the blastula stage of development and the notochord. 20. The study of the blastula and of cell specification has many implications on the field of fertility treatments.
