PLATE 4 



EXPLANATION OF FIGURES 



15 Section through the oral epithelium in the posterior part of the premaxilla 

 region of a 65 mm. embryo showing a bud-like upgrowth of the epithelium. X 560. 



16 Section through posterior part of premaxilla region of same embrj'o 

 showing a detached epithelial bud or cyst. X 560. 



17 Section through dermal cyst in an 82 mm. embryo. X 400. 



18 Section through dermal cyst at birth (108 mm.). The central portion of 

 the cyst is cornified like the peripheral layer of the oral epithelium. X 400. 



690 



