1 ectoderm 2 archenteron (central) 3 endoderm 4 first group mesoderm cells 5 origin first group migrating mesoderm cells 6 origin second group mesoderm cells 7 invagination location
English name: Sea urchin Scientific name: Psammechinus sp. Familia: Echinidae Classis: Echinoidea Phylum: Echinodermata Regnum: Animalia
Individual cells migrate to the inside (4) from the base (5) of the growing archenteron (2) . This first group of migrating mesoderm cells (= mesenchym) will later form the skeleton. A second group of mesoderm cells (6) separates from the upper part of the archenteron. These cells will form the wall of organs of the see urchin. To next stage. One stage back.
