 Cold or heat shock has also been shown to result in unreduced amphibian gametes, though this occurs more commonly in eggs than in sperm.John Gurdon (1958) transplanted intact nuclei from somatic cells to produce diploid eggs in the frog, "Xenopus" (an extension of the work of Briggs and King in 1952) that were able to develop to the tadpole stage.The British scientist J.