Embryological Axis
Blastula: “hollow ball” of embryo cells
Gastrula: gastrulation = indent of cell layer into blastula; forms first gut cavity; opening = blastopore;
Mesoderm develops after gastrulation
Protostomes: (Greek proto = first; stoma = mouth) blastopore becomes mouth
- flatworms, nematodes, mollusks, annelids, arthropods
Deuterostomes: (Greek deuteros = second) blastopore becomes anus