188 



THEORY OF EVOLUTION 



that is neither advantageous nor disadvanta- 

 geous, but indifferent, the chance that it may 

 become established in the race is extremely 

 small, although by good luck such a thing may 

 occur rarely. It makes no difference whether 

 the character in question is a dominant or a 



Reeenl 

 Pleistocene- 

 Upper Pliocene 



ELEPHAS 

 (ateftchtn) 



le/ver Pliocene TETRABE10DON 



ftaNGIROSTIttS STACHJ 



Upper Mtoeene fxtmrtentngchin) 



Htddle Miocene TETRA8ELOOON 



fANCUSTIDENS 5TA&E 



Lover Miocene 



into EurvfM- - Asia 



IOKP Cligocem 



h 

 \ P 



P 



PALAEOMASTOOCI 



FIG. 93. Evolution of elephant's skulls. (After Dendy.) 



