English | English 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. |