Rippenqualle. Habitus des tentakellosen adulten Tieres. Disymmetrische oder biradiale Furchung (typische Ctenophorensymmetrie schon nach den ersten drei Teilungsschritten), Bildung der Mikromeren am animalen Pol aus Ektoplasmamaterial. Keimblätterbildung durch Epibolie. Einwanderung sekundärer Mikromeren am vegetativen Pol. Postembryonale Entwicklung bis zum freien Cydippestadium.

In a series of scenes the embryonic development of the ctenophore Beroë is analysed. The particular pattern of cleavage is demonstrated in top and side views as well. At the 8-cell-stage already the embryo's symmetry axes are the same as in the adult. The fourth cleavage results in 8 macromeres and 8 micromeres on the animal pole, the latter increase rapidly in number and grow down over the macromeres (epiboly). A special feature are so-called vegetative, secondary micromeres, which are produced near the blastoporus by the prospective entoderm cells. A free-swimming larva, the cydipped, leaves the egg jelly.