The primitive germ-cells in this species originate in the ectoderm of the stalk of the gonophore bud and migrate from that position along the ectoderm to the tip of the bud where they pass through the mesogloea into the bell-rudiment. During the growth of the oocyte the surrounding cells are at first annexed, but later the process is one of digestion. Fertilization has not been observed.
The early cleavage stages show a good deal of variation ranging from a perfectly regular type which results in the formation of a regular, hollow blastula to an extremely irregular type in which a blastocoele is never formed. The blastula is followed by a stage in which the embryo consists of a solid mass of cells. This stage arises by a process of modified multipolar budding from the walls of the blastula. The ectoderm is now formed by a process of delamination. The coelenteron appears and the mesogloea is formed between ectoderm and endoderm. The embryo is now saucer-shaped and the solid aboral tentacles are now formed in a ring around its edge. A layer of mesogloea appears across the base of each tentacle. A solid circular rim of endoderm is formed at the bases of the tentacles, and this again is separated from the endoderm lining the coelenteron by another layer of mesogloea. Meanwhile a gradual differentiation has taken place in the ectoderm, giving rise to nematocysts and fixation cells.
The embryo now becomes greatly elongated so that its long axis lies between the oral and aboral poles. Five short oral tentacles are now formed, and the mouth breaks through in the middle of the circle. Having reached this stage the embryo is ready to be set free.