optical cross section at the 16 somite stage at the level of the eye.
At the 12 somite stage, expression is observed at the midbrain-hindbrain boundary, somites, posterior spinal cord, posterior floor plate, caudal tip of the notochord and cells ventral to it (endoderm?). Anteriorly, a strong staining is observed in the telencephalon, in head epidermis and in the optic stalk. A weak expression is observed in the ventral posterior diencephalon. At the 14 somite, expression appear in the retina as well as in the dorsal diencephalon. In the somites Fgf8 expression disappears from the posterior part and is restricted to the anterior cells lining the somitic furrow.