The egg masses of Oxynoe olivacea consists of a gelatinous ribbon, inside which the ovigerous capsules are arranged in an undulating row. The ovigerous capsules are not inter-connected by chalaza. They measure about 133 μm long and 103 μm wide and some contain two embryos. Before the first division, the eggs are 68 μm in diameter. Data on embryonic and larval development are provided, as well as their chronology. Larval development is planctotrophic, and veligers hatch between the fifth and sixth day after oviposition. At the time of hatching, the larval shell measures 100 μm. Metamorphosis could not be observed.