Slide showing photograph of Triton twin embryos as in Fig. 7. Slide showing photograph of Triton twin embryos as in Fig. 7. (UNIVERSITY 1437/2/3/61) Title below image reads: 'Fig. 8. The same operation as in Fig. 7: twins at a later stage in development. (After Spemann, 1928.)' Late 19th to early 20th century