A layer of cells produced during the process of
gastrulation during the early development of the animal embryo, which is distinct from other such layers of cells, as an early step of cell differentiation.
The three types of germ layers are the
endoderm,
ectoderm, and
mesoderm.
germ layer theory: The developmental biology theory that during early development, the animal embryo divides itself into two or three germ layers, each of which then proceed to further differentiate into organs and tissues specific to that particular layer.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.