芽体 is read as がたい (gatai) and means blastema.
がたい
gatai
め
germinal disk (in an egg)
めばえ
bud
めばえる
to arise
めぶく
to bud
がじょうへんい
bud mutation
めだし
sprouting
がせい
gemmation
めがでる
to have luck on one's side
めをだす
to sprout
めだち
がきゅう
blast (cell)
いたい
(dead) body