metazoa

‖n. pl. [ NL., fr. Gr. &unr_; after + zw^, on an animal. ] (Zool.) Those animals in which the protoplasmic mass, constituting the egg, is converted into a multitude of cells, which are metamorphosed into the tissues of the body. A central cavity is commonly developed, and the cells around it are at first arranged in two layers, -- the ectoderm and endoderm. The group comprises nearly all animals except the Protozoa. [ 1913 Webster ]