184 THE MAMMALIA. 



stage is their total disappearance. FurtluT, we 

 then see indications of the brow weapons, in 

 correlation with the loss of the canines. Filhol 

 here reminds us of the proposition expressed 

 even by Aristotle, and formulated again at the 

 beginning of this century by Etienne Geoffroy St. 

 Hilaire with regard to the balancing of the organs 

 (balancement des organes). With the loss of the 

 front premolars, the permanent molars become 

 more regularly developed, and it is thus that the 

 now typical ruminant jaw has been farther and 

 farther developed ; the ancient form owing to 

 complete rows of teeth and the more marked 

 canines still, in some measure, resembled the 

 jaw of the Omnivora and the Bunodonts (animal 

 with tuberculate teeth). 



From Filhol's observations we find that this 

 process of the gradual formation and the fixing of 

 the gap in the dentition of the Euminants has 

 repeated itself that, at first, individual modifica- 

 tions became established by inheritance, and 1< d 

 to the formation of races. And although we 

 cannot, in every instance, trace the given advan- 

 tages connected with the modifications, and that 

 led to the selection, still, as was shown above, we 

 have some idea, as well as some explanation, of 



