This is reported to extend from mid- to late summer. Active planulae, obtained in the above manner will readily attach and metamorphose as far as the scyphula stage, if they are placed in clean watch glasses of sea water. The pinkish, transparent eggs measure about 120 microns in diameter. Fertilization occurs in the gastric pouches, and the eggs are transferred to small brood-pouches on the inner surfaces of the oral arms. Cleavage is total and quite regular, forming a hollow, single-layered blastula.
Gastrulation is by invagination, occasionally accompanied by an in-wandering of cells.
At the time of completion of the gastrulation process, the blastopore, which becomes the mouth of the scyphistoma, is almost completely closed. The mouth and a short hypostome soon become visible. The tentacle number is increased to 24 in about a month. Lateral buds can be produced, which either become free or form stolons from which new scyphistomae arise. In the older scyphistomae, the gastric pouches can be seen to communicate by means of holes in the taeniolae, forming the ring sinus just below the oral disc.