CHAPTER X. 



Linear Series — continued. 

 Teeth — Recapitulation. 



In this chapter I propose to speak of those matters which seem 

 to have most consequence in the foregoing evidence as to the 

 Variation of Teeth. Each of the following sections treats of some 

 one such subject, specifying the cases which chiefly illustrate it. 

 It will be understood that the sections do not stand in any logical 

 collocation but are simply arranged consecutively. The treatment 

 given is of course only provisional and suggestive, being intended 

 to emphasize those points which may repay investigation. 



The subjects which especially call for remark are as follows : 



(1) The comparative frequency of dental Variation in differ- 



ent animals. 



(2) Symmetry in Meristic Variation of Teeth. 



(3) Division of Teeth. 



(4) Duplicate Teeth. 



(5) Presence and absence of Teeth standing at the ends of 



series (first premolars, last molars). 



(6) The least size of particular Teeth. 



(7) Homceotic Variation in terminal Teeth when a new 



member is added behind them. 



(8) Reconstitution of parts of the Series. 



(1) The comparative frequency of dental Variation in different 



animals. 



The total number of skulls examined for the purpose of this 

 inquiry was about 3000. From so small a number it is clearly 

 impossible to make any definite statement as to the relative 

 frequency of Variation in the different orders, but some indications 

 of a general character may be legitimately drawn. 



First, the statistics very clearly shew that while dental Varia- 

 tion is rare in some forms, it is comparatively frequent in others, 

 but there is no indication that this frequency depends on any 

 condition or quality common to these forms. Setting aside 

 examples of the coming and going of certain small and variable 



