8 



ON THE ORIGIN AND DEVELOPMENT OF THE 



of the labial mucous membrane. There was a labial frenum. 

 The breadth of the superior arch was If line ; length li. 



4. The jaws of an embryo nine weeks old were examined 

 under water. 



Upper Jaw. No material change had taken place in the 

 configuration of the palate, except that 

 the median lobule (ra, Fig. 8), had di- 

 minished relatively, and in the trans- 

 verse direction, while the lateral 

 lobules (n) had increased relatively, 

 and also in the transverse direction. 

 A longitudinal lobule (y), had also 

 appeared on the surface of the 

 median lobule (m). The cleft 

 (x) in the soft palate was smaller. 

 The posterior part of the dental groove was wider. The 

 papilla (1), had become more prominent, and the lips of 

 the groove had almost met before and behind it. The papilla 

 (2) is larger. A little further on, corresponding with the 

 lateral lobule (n\ on each side, two papillae (3 and 4), with 

 notched laminse in front of them, had appeared. The centrals 

 (3), or those on each side of the median line, were the 

 most distinct. 



Lower Jaw. The lips of the dental groove had approached 

 so as to require separation by the 

 needle to exhibit its contents dis- 

 tinctly. The papilla (1 or 2, Fig. 9) 

 had undergone little change, but two 

 very indistinct bulgings (3 and 4) 

 had appeared on each side of the 

 labial frenum, the centrals (3) being the Fig. 9. 



largest. The breadth of the superior arch was If line ; the 

 length 1-J line. 



