Sucker induction in Xenopus: Xenopus laevis embryos, at late blastula stage, were cut in order to separate the blastocelic roof from the other parts of the embryo (Fig. 1). Ectoderm cell explants obtained in this way were cultured in Holtfreter's solution for 100 hours at 18°C; we called these explants controls. Treated explants were cultured for 18 hours at 18°C in Holtfreter's solution containing 25 mM NaSCN or 50 mM urea, and then they were transferred and left for 82 hours more in Holtfreter's solution. After 100 hours of culture, control explants developed atypical epidermis and only 11.6% of them showed very small suckers (Table 1, Figs 4, 5); on the contrary 48% of treated explants, at the end of the culture period, formed large suckers (Table 1, Figs 6, 8), even bigger than those of the embryos of the same age (Table 1, Fig. 2). The bigger volume of treated explant suckers was due to an increase in cell number. The suckers formed in treated explants are well developed, even if their cells are not so elongated as the control ones, and not so well differentiated (Table 1, Figs 3, 7, 9). We conclude that it is possible to obtain sucker induction using NaSCN or urea which are both well-known neural inductors. Similar results were obtained (Picard, 1975) in ectodermic cell explants from Xenopus gastrula by treatment with $10^{-4}M$$NH_{4}Cl$.