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	...	Discussion The purpose of this experiment was to explore the development of spicules in the sea urchin larval skeleton. NiCl2 interferes with spicule and skeletal formation by interfering with the migration of the primary mesenchyme cells. By introducing half of the embryos into a solution of NiCl2, we observed the effects of blocking the skeleton formation. In normal embryos, the spicules can be stained with Ig8 and visualized with polarized light (Fig. 2&3). In the experimental group, none of the embryos undergone complete gastrulation; the Ig8 staining showed that the PMCs failed to migrate and cluster (Fig.4). Our original hope, that we could block skeleton formation in the urchin, was satisfied by this experiment. In conclusion, the Ig8 staining of the spicules and polarized light helped us determine that NiCl2disrupts not only skeleton formation, but the process of gastrulation as well. References: - Influence of NiCl2on the Skeleton Formation in Sea Urchin: Armstrong, N, J Hardin, DR McClay. (1993) Cell-cell interactions regulate skeleton formation in the sea urchin embryo. Development 119:833-840; Hardin, J, JA Coffman, SD Black, DR McClay. (1992) Commitment along the dorsoventral axis of the sea urchin is altered in response to NiCl2. Development 116:671-685. Guss, Kirsten A., and Ettensohn, Charles A. (1997) Skeletal morphogenesis in the sea urchin embryo: regulation of primary mesenchyme gene expression and skeletal rod growth by ectoderm-derived cues. Development 124: 1899-1908. Wray, G.A., and McClay, D.R. (1988) The Origin of Spicule-Forming Cells in a Primitive Sea Urchin Eucidaris-Tribuloides Which Appears to Lack Primary Mesenchyme Cells. Development 103: 302-316.   - Basics of Sea Urchin Development. Gilbert SF. editor. 2010. Developmental biology. 9th ed.: Sinauer Associates, Inc., Sunderland, Mass, 918 p.