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Webster 1913 Edition
Metazoa
‖
Metˊa-zo′a
,Noun.
pl.
[NL., fr. Gr. [GREEK] after +
ζῶ,ον
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.