"Modes of forming mesoderm. A and B, special mesoblasts distinguishable early in egmentation (annelid): A, surface view from active pole; B, sectional view of same. ec, micromeres destined to form ectoderm; en, macromeres destined to form entoderm; m, primitive mesoblast which produces the mesoderm. C, amaeboid mesodermal cells (c) budding from entoderm into the segmentation cavity (s.c.), in an Echinoderm. a, archenteron." — Galloway

Mesoderm

"Modes of forming mesoderm. A and B, special mesoblasts distinguishable early in egmentation (annelid):…