A middle layer of
tissue in a developing
animal embryo which will eventually become the
muscles and other
connective tissues, the
blood vessels and
blood cells (if any), and various other
organs,
structures, and
systems (depends on the
organism). Animals with this layer of
tissue as an
embryo are known as
triploblastic animals, which includes all animals except for
sponges,
placozoans,
jellyfish, and
comb jellies.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.