A Human Embryo of Streeter Age Group XVIII

A human embryo was serially sectioned and was reconstructed with the 634 sections. The presumptive length of the embryo was 14mm. This embryo was characterized by the heavy pigmentation of retina, loss of lens vesicle, three semicircular ducts and still L-shaped cochlea at the inner ear, formation of the vomeronasal organ, recognition of nasolacrimal duct , secondary branches from the stem bronchi in the lung , separation of right and left ventricles but the absence of septum membranaceum, and the formation of the Mullerian duct From above findings , we concluded that this embryo belonged to the early stage of age group XVIII of Streeters developmental horizo