DEVELOPMENT OF THE TEETH IN MAMMALIA 39 



The enamel crypt is a niche enclosed laterally by the 

 lateral ledge, and its floor is formed by the top of the enamel 

 organ. 



The enamel septum. Two centres are described for the 

 differentiation of the enamel pulp (or stellate reticulum) 

 a mesial or lingual and a lateral or buccal. An area of 

 undifferentiated cells forms a septum between these two 

 centres, and stretches from the external epithelium of the 

 enamel organ to the stratum intermedium, dividing the body 



FIG. 11. Enamel organ of Macropus, showing division of stellate 

 reticulum into two portions. The enamel septum of Bolk. ( x 225.) 



of the enamel organ into a mesial and a lateral portion 

 (see figs 11,12). 



The enamel navel, as this author calls it, is a groove or 

 depression in the external epithelium of the enamel organ 

 at the point where the septum touches this layer ' This 

 groove ', he considers, ' further accentuates the division of 

 the enamel organ into a mesial and a lateral half, suggested 

 by the septum.' 



Marett Tims and Hopewell Smith describe and figure in 

 the enamel organ of a Wallaby a division into two parts, 

 but are uncertain whether to interpret it as the fusion of 



