(A) Gastrula (left side view). (B) Anatomical distribution of each cluster in gastrulae. (C) An early larva, left side view. (D) Anatomical distribution of each cluster in early larvae. Cluster numbers are shown with corresponding germ layers, organs, and tissues. This figure shows that for examples cells of cluster 8 comprise apical plate and cells of cluster 9 comprise coelom, a mesodermal derivative.

Both chordate neural plate and ambulacrarian ciliary bands develop using a similar set of genes, suggesting these two organs are homologous.

(A) Expression profiles of development-relevant genes in the stomodeal (mouth opening) region. The stomodeum is formed by stomodeal ectoderm (orange), stomodeal endoderm (blue) and oral endoderm (green). Most of genes expressed in these regions are major component genes of vertebrate Spemann’s organizer. (B) (Left) Gene expression pattern of chordate dorsal structures (notochord + floor plate), and (right) that of starfish larval stomodeum, transverse section of dotted line of (A). This suggests the ambulacrarian stomodeum plays a role of vertebrate Spemann’s organizer.

A starfish, also known by the scientific name Patiria pectinifera.