422 DEVELOPMENT OF ORGAJfS IN MAMMALIA. [XII. 



which according to most authors give rise to the enarael 

 and dentine respectively. 



The proctodsemn. The cloaca! section of the ali- 

 mentary canal is placed in communication with the 

 exterior by means of a shallow epiblastic invagination 

 constituting the proctodjeum. 



