541 



region of this tooth be examined in the Dog, three separate down- 

 growths of the dental lamina will be noticed, from the central one of 

 which the functional first premolar is seen to be developing. 



Now as downgrowths of the dental lamina which I regard as re- 

 presenting the deciduous, successional and post - permanent dentitions 

 are to be found in 

 other parts of the 

 jaw, I think it is 

 only reasonable to 

 infer that they are 



the same series 

 throughout. From 

 this I conclude that 

 when pm^ is pre- 

 sent in one denti- 

 tion only, it belongs, 

 most probably , to 



that commonly 

 spoken of as the 

 permanent or suc- 

 cessional. 



Pig. 2. FA!^ of Dog 3 days old — shewing developing Tooth with Lingual (a) and 

 Labial (b) Down growths of the Dental Lamina. 



Labial side 



Fig. 3. Section through First upper Premolar of fcetal Pig. 



