In continuing a comprehensive study of the stapedial region of the human ear, special attention has been given to the stapes, the vestibular window and the associated fissular tracts in developmentally important embryonic and fetal stages. In a preceding article1 the steps in morphogenesis were traced as encountered in specimens from 6.7 to 50 mm. in crown-rump length; the current article carries the account through the 150 mm. specimen, at which stage the formation of bone is initiated in the stapes. Both of the contributions just referred to serve to fill hiatuses existing in two more general papers on stapedial, fissular and fenestral anatomy.2
MATERIAL AND METHODS
For this stage of the investigation reconstructions of the stapes, together with the surrounding area, were prepared by the wax plate method of Born.3 Representative developmental stages were selected for reconstruction at approximately 25 mm. intervals, while comparable or additional anatomic features in