Sea Urchins -Advanced Protocols UV treatment of embryos- method 1; method 2 UV treatment of sea urchin sperm Inhibition of the blocks to polyspermy Induction of polyspermy by treatment with nicotine LiCl2 treatment NiCl2 treatment The effect of sulfate-deprivation on gastrulation The effect of exposure to copper chloride The requirement for calcium during gastrulation Separation of blastomeres-1, 2 The effect of temperature on early development-1, 2 The effect of exposure to saccharine on sea urchin development