The study of enzymic activities found in hen eggs had started in the early years of this century and have become refined and steady in relation to the development of enzyme kinetics and protein chemistry. About 30 kinds of enzymic activities have so far been found in unfertilized hen eggs and, in some cases, enzymes have been purified to homogeneity and the biochemical, enzymological properties, and, even if to a lesser extent, the biological significance clarified.