674 



BERTHA E. MARTIN 



this connection about .68 mm. back of the front end of the 

 maxilla. After becoming disconnected from the oral epithelium, 

 the dental lamina is much reduced in size and extends through 

 the substance of the jaw in the form of an irregular oval cord of 

 cells. In a 50 mm. embryo, the posterior end of the premaxilla 

 slightly overlaps the anterior end of the maxilla. Here and 

 there in this region of overlapping, the scattered remnants of 



Fig. 15 Diagr;imuuiti(' sections through posterior part of preniaxilhi of a 

 55 mm. embryo showing the formation of the epithelial buds which are destined 

 to give rise to the dermal cysts shown in plate 4, figures 16 to 18. 



the dental lamina occur. A similar condition was found in a 

 60 mm. embryo. But in a 55 mm. embryo which was apparently 

 better developed than the 60 mm. embryo, I discovered two 

 features which are of great interest in the light of subsequent 

 results. Figure 15 shows a series of diagrams through the pos- 

 terior part of the premaxilla and in that region of the dental 

 ridge in which farther back in the jaw is a slight, upward growth 

 of the oral epithelium. In the next two sections, 15, h, and 15, c, 

 this epithelial bud is no longer connected with the oral epithe- 



