Holtfreter (1934) and Needham et al (1934) have shown that embryonic inductions can be obtained if material from the crushed or centrifuged ovarian egg is implanted, after coagulation, into the blastocoel of newt gastrulae. It is therefore clear that the evocator substance is contained in the egg before fertilization. Now Duryee (1937) has recently drawn attention to the fact that it is easy to isolate the nucleus of the ovarian egg, and it seemed interesting to determine whether the evocator is contained in the nucleus or whether it is a purely cytoplasmic constituent of the egg-cell.
Nuclei were removed from ovarian eggs of either Triton alpestris or T. taeniatus. Some implantations were made with isolated living nuclei, but the results were unsatisfactory; the operated embryos always appeared to be entirely normal and on sectioning showed no sign of the implanted nucleus, which presumably had ruptured and been absorbed. It...
